.gitignore                                       |   6 ++++++
 COPYING                                          | 661 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 Documentation/design_notes.txt                   |  67 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 Makefile.PL                                      |  38 ++++++++++++++++++++++++++++++++++++++
 README                                           | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/PublicInbox/Filter.pm                        | 216 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 public-inbox-mda                                 |  51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 sa_config/Makefile                               |  17 +++++++++++++++++
 sa_config/README                                 |  19 +++++++++++++++++++
 sa_config/root/etc/spamassassin/public-inbox.pre |   9 +++++++++
 sa_config/user/.spamassassin/user_prefs          |  26 ++++++++++++++++++++++++++
 scripts/dc-dlvr                                  |  64 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 scripts/import_gmane_spool                       |  51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 scripts/report-spam                              |  28 ++++++++++++++++++++++++++++
 t/filter.t                                       | 262 +++++++++++++++++++++++++++++++++++++++++++++++++++++

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000000000000000000000000000000000000..e262bd599ddbdbc79f87fd2a13eebff218a486ba
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+/Makefile.old
+/pm_to_blib
+/MYMETA.yml
+/Makefile
+/blib
+/cover_db
diff --git a/COPYING b/COPYING
new file mode 100644
index 0000000000000000000000000000000000000000..dba13ed2ddf783ee8118c6a581dbf75305f816a3
--- /dev/null
+++ b/COPYING
@@ -0,0 +1,661 @@
+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU Affero General Public License is a free, copyleft license for
+software and other kinds of works, specifically designed to ensure
+cooperation with the community in the case of network server software.
+
+  The licenses for most software and other practical works are designed
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+our General Public Licenses are intended to guarantee your freedom to
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+software for all its users.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
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+want it, that you can change the software or use pieces of it in new
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+
+  Developers that use our General Public Licenses protect your rights
+with two steps: (1) assert copyright on the software, and (2) offer
+you this License which gives you legal permission to copy, distribute
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+The GNU General Public License permits making a modified version and
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+  An older license, called the Affero General Public License and
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+  The precise terms and conditions for copying, distribution and
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+
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+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
+Foundation.  If the Program does not specify a version number of the
+GNU Affero General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU Affero General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<http://www.gnu.org/licenses/>.
diff --git a/Documentation/design_notes.txt b/Documentation/design_notes.txt
new file mode 100644
index 0000000000000000000000000000000000000000..8ec1d369f1c58c6a485d0de2576775a3a60dc687
--- /dev/null
+++ b/Documentation/design_notes.txt
@@ -0,0 +1,67 @@
+Design notes and philosophy
+---------------------------
+
+Challenges to running normal mailing lists
+------------------------------------------
+1) spam
+2) bounce processing of invalid/bad email addresses
+3) processing subscribe/unsubscribe requests
+
+Issues 2) and 3) are side-stepped entirely by moving reader
+subscriptions to git repository synchronization and Atom feeds.  There's
+no chance of faked subscription requests and no need to deal with
+confused users who cannot unsubscribe.
+
+Use existing infrastructure
+---------------------------
+
+* public-inbox can coexist with existing mailing lists, any subscriber
+  to the existing mailing list can begin delivering messages to
+  public-inbox-mda(1)
+
+* public-inbox uses SMTP for posting.  Posting a message to a public-inbox
+  instance is no different than sending a message to any open mailing
+  list.
+
+* readers may continue using use their choice of mail clients and
+  mailbox formats, only learning a few commands of the ssoma(1) tool
+  is required.
+
+* Atom is a reasonable feed format for casual readers and is supported
+  by a variety of feed readers.
+
+Why email?
+----------
+
+* Freedom from proprietary services, tools and APIs.  Communicating with
+  developers and users of Free Software should not rely on proprietary
+  tools or services.
+
+* Existing infrastrucuture, tools, and user familarity.
+  There is already a large variety of tools, clients, and email providers
+  available.  There are also many resources for users to run their own
+  SMTP server on a domain they control.
+
+* All public discussion mediums are affected by spam and advertising.
+  There exist several good Free Software anti-spam tools for email.
+
+* Privacy is not an issue for public discussion.  Public mailing list
+  archives are common and accepted by Free Software communities.
+  There is no need to ask the NSA for backups of your mail archives :)
+
+* git, one of the most widely-used version control systems, includes many
+  tools for for email: git-format-patch(1), git-send-email(1), git-am(1).
+  Furthermore, the development of git itself is based on the git mailing
+  list.
+
+* Email is already the de-facto form of communication in many Free Software
+  communities.
+
+* Fallback/transition to private email and other lists, in case the
+  public-inbox host becomes unavailable, users may still directly email
+  each other (or Cc: lists for related/dependent projects).
+
+Copyright
+---------
+Copyright 2013, Eric Wong <normalperson@yhbt.net> and all contributors.
+License: AGPLv3 or later <http://www.gnu.org/licenses/agpl-3.0.txt>
diff --git a/Makefile.PL b/Makefile.PL
new file mode 100644
index 0000000000000000000000000000000000000000..e7aea949688e71638cf50b11b68106ba5d3c5310
--- /dev/null
+++ b/Makefile.PL
@@ -0,0 +1,38 @@
+#!/usr/bin/perl -w
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: AGPLv3 or later (https://www.gnu.org/licenses/agpl-3.0.txt)
+use strict;
+use ExtUtils::MakeMaker;
+WriteMakefile(
+	NAME => 'public-inbox',
+	VERSION => '0.0.0',
+	AUTHOR => 'Eric Wong <normalperson@yhbt.net>',
+	ABSTRACT => 'public-inbox.org infrastructure',
+	EXE_FILES => [qw/public-inbox-mda/],
+	PREREQ_PM => {
+	        # note: we use ssoma(1) and spamc(1),
+		# NOT the Perl modules
+		'Email::MIME' => 0,
+		'Email::MIME::ContentType' => 0,
+		'Email::Filter' => 0,
+	},
+);
+
+sub MY::postamble {
+  <<'EOF';
+RSYNC_DEST = public-inbox.org:/srv/public-inbox/
+docs = README COPYING $(shell git ls-files Documentation/ '*.txt')
+gz_docs = $(addsuffix .gz, $(docs))
+%.gz: %
+	gzip -9 --rsyncable < $< > $@+
+	touch -r $< $@+
+	mv $@+ $@
+
+gz-docs: $(gz_docs)
+rsync-docs:
+	git set-file-times $(docs)
+	$(MAKE) gz-docs
+	rsync --chmod=Fugo=r -av $(gz_docs) $(docs) $(RSYNC_DEST)
+
+EOF
+}
diff --git a/README b/README
new file mode 100644
index 0000000000000000000000000000000000000000..71643dcc05d076de6f6732e30995ba1039961ecd
--- /dev/null
+++ b/README
@@ -0,0 +1,145 @@
+public-inbox - shared mailboxes via git for public discussion
+-------------------------------------------------------------
+
+public-inbox implements the sharing of an email inbox to complement or
+replace traditional mailing lists for public discussion.  public-inbox
+is primarily intended as a Free, distributed (but not yet decentralized)
+public communications tool for users and developers of Free and Open
+Source Software.  public-inbox should be easy-to-deploy and manage;
+encouraging software projects to run their own instances with minimal
+overhead.
+
+Implementation
+--------------
+public-inbox uses ssoma[1], Some Sort Of Mail Archiver which implements
+no policy of its own.  By exposing an inbox via git, readers may follow
+the mailing list without subscribing and have easy access to historical
+messages.
+
+Traditional mailing lists use the "push" model.  List servers deliver
+content via SMTP to other mail servers used by readers of the mailing
+list.  For readers, this requires commitment to subscribe to the list
+and extra effort to unsubscribe.  Readers may also have difficulty
+following discussions which started before they joined if archives do
+not expose Message-Id headers for responses.  For list server admins,
+this also burdens them with bounce/failure messages for bad/invalid
+addresses.
+
+public-inbox uses the "pull" model.  Readers import mail into an mbox,
+Maildir, or IMAP folder from the git repositories periodically.  If a
+reader loses interest, they simply stop syncing.  Since ssoma uses git,
+mirrors are easy-to-setup, and lists are easy-to-relocate to different
+mail addresses without losing/splitting archives.  Readers only need
+to install ssoma, a command-line tool[1] currently implemented in Perl.
+
+Readers may also follow the list via Atom feed.
+
+[1] http://ssoma.public-inbox.org/
+
+Features
+--------
+* stores email in git, so readers have a full history of the mailing list
+* Atom feed allows casual readers to follow via feed reader
+* Mail user-agent (MUA) users may use Maildir, mbox(5) and/or IMAP locally
+* uses only well-documented and easy-to-implement data formats
+
+Requirements (Atom, read-only client)
+-------------------------------------
+* any feed reader capable of following Atom feeds
+
+Requirements (server MDA)
+-------------------------
+* git
+* MTA - postfix is recommended
+* Perl and several modules:
+    - Email::Filter
+    - XML::Atom::SimpleFeed
+* Ssoma - currently a Perl module
+* SpamAssassin (optional, recommended)
+* any HTTP server (optional, for serving Atom feed)
+
+Hacking
+-------
+Source code is available via git:
+
+	git clone git://bogomips.org/public-inbox
+
+See below for contact info.
+
+Contact
+-------
+We are happy to see feedback of all types via plain-text email.
+public-inbox discussion is self-hosting on public-inbox.org
+Please send comments, user/developer discussion, patches, bug reports,
+and pull requests to our public-inbox.org address at:
+
+	public-inbox@public-inbox.org
+
+Please Cc: all recipients when replying as we do not require
+subscription.  This also makes it easier to rope in folks of
+tangentially related projects we depend on (e.g. git developers on
+git@vger.kernel.org).
+
+You can subscribe via ssoma(1), LISTNAME is a name of your choosing:
+
+    URL=git://git.public-inbox.org/public-inbox
+    LISTNAME=public-inbox
+
+    # to initialize a maildir (this may be a new or existing maildir,
+    # ssoma will not touch existing messages)
+    # If you prefer mbox, use "ssoma add mbox ..." instead
+    ssoma add $LISTNAME $URL maildir:/path/to/maildir/
+
+    # read with your favorite MUA (only using mutt as an example)
+    mutt -f /path/to/maildir # (or /path/to/mbox)
+
+    # to keep your mbox or maildir up-to-date, periodically run the following:
+    ssoma sync $LISTNAME
+
+    # your MUA may modify and delete messages from the maildir or mbox,
+    # this does not affect ssoma functionality at all
+
+    # to sync all your ssoma subscriptions
+    ssoma sync
+
+Anti-Spam
+---------
+The maintainer of public-inbox has found SpamAssassin a good tool for
+filtering his personal mail, and it will be the default spam filtering
+tool in public-inbox.
+
+Readers may also use a custom mail-delivery-agent for delivery to enable
+spam filtering by having ssoma deliver to a command via pipe.
+
+There is unlikely to be any tool which is 100% accurate at classifying
+spam, so it is possible to remove messages using the ssoma-rm(1) tool
+in ssoma.
+
+Content Filtering
+-----------------
+To discourage phishing, web bugs (tracking), viruses and other nuisances,
+only plain-text content is allowed by default and non-text content is
+stripped.  This saves I/O bandwidth and storage, which is important as
+entire mail archives are shared between clients.
+
+As of the 2010s, successful online social networks and forums are the
+ones which heavily restrict users formatting options; so public-inbox
+aims to preserve the focus on content, and not presentation.
+
+Copyright
+---------
+Copyright 2013, Eric Wong <normalperson@yhbt.net> and all contributors.
+License: AGPLv3 or later <http://www.gnu.org/licenses/agpl-3.0.txt>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
diff --git a/lib/PublicInbox/Filter.pm b/lib/PublicInbox/Filter.pm
new file mode 100644
index 0000000000000000000000000000000000000000..6cccd930862c363ab61393d05158e53ceb8b382a
--- /dev/null
+++ b/lib/PublicInbox/Filter.pm
@@ -0,0 +1,216 @@
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: AGPLv3 or later (https://www.gnu.org/licenses/agpl-3.0.txt)
+#
+# This only exposes one function: run
+# Note: the settings here are highly opinionated.  Obviously, this is
+# Free Software (AGPLv3), so you may change it if you host yourself.
+package PublicInbox::Filter;
+use strict;
+use warnings;
+use Email::MIME;
+use Email::MIME::ContentType qw/parse_content_type/;
+use Email::Filter;
+use IPC::Open2;
+our $VERSION = '0.0.1';
+
+# start with the same defaults as mailman
+our $BAD_EXT = qr/\.(?:exe|bat|cmd|com|pif|scr|vbs|cpl)\z/i;
+
+# this is highly opinionated delivery
+# returns 0 only if there is nothing to deliver
+sub run {
+	my ($class, $simple) = @_;
+
+	my $content_type = $simple->header("Content-Type") || "text/plain";
+
+	# kill potentially bad/confusing headers
+	# Note: ssoma already does this, but since we mangle the message,
+	# we should do this before it gets to ssoma.
+	foreach my $d (qw(status lines content-length)) {
+		$simple->header_set($d);
+	}
+
+	if ($content_type =~ m!\btext/plain\b!i) {
+		return 1; # yay, nothing to do
+	} elsif ($content_type =~ m!\btext/html\b!i) {
+		# HTML-only, non-multipart
+		my $body = $simple->body;
+		my $ct_parsed = parse_content_type($content_type);
+		dump_html($body, $ct_parsed->{attributes}->{charset});
+		replace_body($simple, $body);
+		return 1;
+	} elsif ($content_type =~ m!\bmultipart/!i) {
+		return strip_multipart($simple, $content_type);
+	} else {
+		replace_body($simple, "$content_type message scrubbed");
+		return 0;
+	}
+}
+
+sub replace_part {
+	my ($simple, $part, $type) = ($_[0], $_[1], $_[3]);
+	# don't copy $_[2], that's the body (it may be huge)
+
+	# Email::MIME insists on setting Date:, so just set it consistently
+	# to avoid conflicts to avoid git merge conflicts in a split brain
+	# situation.
+	unless (defined $part->header('Date')) {
+		my $date = $simple->header('Date') ||
+		           'Thu, 01 Jan 1970 00:00:00 +0000';
+		$part->header_set('Date', $date);
+	}
+
+	$part->charset_set(undef);
+	$part->name_set(undef);
+	$part->filename_set(undef);
+	$part->format_set(undef);
+	$part->encoding_set('8bit');
+	$part->disposition_set(undef);
+	$part->content_type_set($type);
+	$part->body_set($_[2]);
+}
+
+# converts one part of a multipart message to text
+sub html_part_to_text {
+	my ($simple, $part) = @_;
+	my $body = $part->body;
+	my $ct_parsed = parse_content_type($part->content_type);
+	dump_html($body, $ct_parsed->{attributes}->{charset});
+	replace_part($simple, $part, $body, 'text/plain');
+}
+
+# modifies $_[0] in place
+sub dump_html {
+	my $charset = $_[1] || 'US-ASCII';
+	my $cmd = "lynx -stdin -dump";
+
+	# be careful about remote command injection!
+	if ($charset =~ /\A[A-Za-z0-9\-]+\z/) {
+		$cmd .= " -assume_charset=$charset";
+	}
+
+	my $pid = open2(my $out, my $in, $cmd);
+	print $in $_[0];
+	close $in;
+	{
+		local $/;
+		$_[0] = <$out>;
+	}
+	waitpid($pid, 0);
+}
+
+# this is to correct user errors and not expected to cover all corner cases
+# if users don't want to hit this, they should be sending text/plain messages
+# unfortunately, too many people send HTML mail and we'll attempt to convert
+# it to something safer, smaller and harder-to-track.
+sub strip_multipart {
+	my ($simple, $content_type) = @_;
+	my $mime = Email::MIME->new($simple->as_string);
+
+	my (@html, @keep);
+	my $rejected = 0;
+	my $ok = 1;
+
+	# scan through all parts once
+	$mime->walk_parts(sub {
+		my ($part) = @_;
+		return if $part->subparts; # walk_parts already recurses
+
+		# some extensions are just bad, reject them outright
+		my $fn = $part->filename;
+		if (defined($fn) && $fn =~ $BAD_EXT) {
+			$rejected++;
+			return;
+		}
+
+		my $part_type = $part->content_type;
+		if ($part_type =~ m!\btext/plain\b!i) {
+			push @keep, $part;
+		} elsif ($part_type =~ m!\btext/html\b!i) {
+			push @html, $part;
+		} elsif ($part_type =~ m!\btext/[a-z0-9\+\._-]+\b!i) {
+			# Give other text attachments the benefit of the doubt,
+			# here?  Could be source code or script the user wants
+			# help with.
+
+			push @keep, $part;
+		} else {
+			# reject everything else
+			#
+			# Yes, we drop GPG/PGP signatures because:
+			# * hardly anybody bothers to verify signatures
+			# * we strip/convert HTML parts, which could invalidate
+			#   the signature
+			# * they increase the size of messages greatly
+			#   (especially short ones)
+			# * they do not compress well
+			#
+			# Instead, rely on soft verification measures:
+			# * content of the message is most important
+			# * we encourage Cc: all replies, so replies go to
+			#   the original sender
+			# * Received, User-Agent, and similar headers
+			#   (this is also to encourage using self-hosted mail
+			#   servers (using 100% Free Software, of course :)
+			#
+			# Furthermore, identity theft is uncommon in Free/Open
+			# Source, even in communities where signatures are rare.
+			$rejected++;
+		}
+	});
+
+	if ($content_type =~ m!\bmultipart/alternative\b!i) {
+		if (scalar @keep == 1) {
+			return collapse($simple, $keep[0]);
+		}
+	} else { # convert HTML parts to plain text
+		foreach my $part (@html) {
+			html_part_to_text($simple, $part);
+			push @keep, $part;
+		}
+	}
+
+	if (@keep == 0) {
+		@keep = (Email::MIME->create(
+			attributes => {
+				content_type => 'text/plain',
+				charset => 'US-ASCII',
+				encoding => '8bit',
+			},
+			body_str => 'all attachments scrubbed by '. __PACKAGE__
+		));
+		$ok = 0;
+	}
+	if (scalar(@html) || $rejected) {
+		$mime->parts_set(\@keep);
+		$simple->body_set($mime->body_raw);
+		mark_changed($simple);
+	} # else: no changes
+
+	return $ok;
+}
+
+sub mark_changed {
+	my ($simple) = @_;
+	$simple->header_set("X-Content-Filtered-By", __PACKAGE__ ." $VERSION");
+}
+
+sub collapse {
+	my ($simple, $part) = @_;
+	$simple->header_set("Content-Type", $part->content_type);
+	$simple->body_set($part->body_raw);
+	mark_changed($simple);
+	return 1;
+}
+
+sub replace_body {
+	my $simple = $_[0];
+	$simple->body_set($_[1]);
+	$simple->header_set("Content-Type", "text/plain");
+	if ($simple->header("Content-Transfer-Encoding")) {
+		$simple->header_set("Content-Transfer-Encoding", undef);
+	}
+	mark_changed($simple);
+}
+
+1;
diff --git a/public-inbox-mda b/public-inbox-mda
new file mode 100755
index 0000000000000000000000000000000000000000..4e971d920db9bfbf2c9552fa43766f6b559e4bbb
--- /dev/null
+++ b/public-inbox-mda
@@ -0,0 +1,51 @@
+#!/usr/bin/perl -w
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: AGPLv3 or later (https://www.gnu.org/licenses/agpl-3.0.txt)
+use strict;
+use warnings;
+use Email::Filter;
+use PublicInbox::Filter;
+use IPC::Run qw(run);
+my $usage = "public-inbox-mda main_repo fail_repo < rfc2822_message";
+my $filter = Email::Filter->new(emergency => "~/emergency.mbox");
+my $main_repo = shift @ARGV or die "Usage: $usage\n";
+my $fail_repo = shift @ARGV or die "Usage: $usage\n";
+
+my $filtered;
+if (do_spamc($filter->simple, \$filtered)) {
+	# update our message with SA headers (in case our filter rejects it)
+	my $simple = Email::Simple->new($filtered);
+	$filtered = undef;
+	$filter->simple($simple);
+
+	if (PublicInbox::Filter->run($simple)) {
+		# run spamc again on the HTML-free message
+		if (do_spamc($simple, \$filtered)) {
+			$filter->simple(Email::Simple->new($filtered));
+			$filter->pipe("ssoma-mda", $main_repo);
+		} else {
+			$filter->pipe("ssoma-mda", $fail_repo);
+		}
+	} else {
+		# PublicInbox::Filter nuked everything, oops :x
+		$filter->pipe("ssoma-mda", $fail_repo);
+	}
+} else {
+	# if SA thinks it's spam or there's an error:
+	# don't bother with our own filtering
+	$filter->pipe("ssoma-mda", $fail_repo);
+}
+die "Email::Filter failed to exit\n";
+
+# we depend on "report_safe 0" in /etc/spamassassin/*.cf with --headers
+# not using Email::Filter->pipe here since we want the stdout of
+# the command even on failure (spamc will set $? on error).
+sub do_spamc {
+	my ($simple, $out) = @_;
+	eval {
+		my $orig = $simple->as_string;
+		run([qw/spamc -E --headers/], \$orig, $out);
+	};
+
+	return ($@ || $? || !defined($$out) || length($$out) == 0) ? 0 : 1;
+}
diff --git a/sa_config/Makefile b/sa_config/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..a90c857f696196a7b80bf1f5e5393259ff6d5d21
--- /dev/null
+++ b/sa_config/Makefile
@@ -0,0 +1,17 @@
+INSTALL = install
+all::
+	@cat README
+
+ROOT_FILES = etc/spamassassin/public-inbox.pre
+install-root:
+	@mkdir -p /etc/spamassassin
+	for f in $(ROOT_FILES); do $(INSTALL) -m 0644 root/$$f /$$f; done
+diff-root:
+	for f in $(ROOT_FILES); do diff -u root/$$f /$$f; done
+
+USER_FILES = .spamassassin/user_prefs
+install-user:
+	@mkdir -p ~/.spamassassin/
+	for f in $(USER_FILES); do $(INSTALL) -m 0644 user/$$f ~/$$f; done
+diff-user:
+	for f in $(USER_FILES); do diff -u user/$$f ~/$$f; done
diff --git a/sa_config/README b/sa_config/README
new file mode 100644
index 0000000000000000000000000000000000000000..6703c38fe1ae74011fcf123e438bc3d9033fc5c1
--- /dev/null
+++ b/sa_config/README
@@ -0,0 +1,19 @@
+SpamAssassin configs for public-inbox.org
+-----------------------------------------
+
+root/ - files for system-wide use (plugins, rule definitions,
+        new rules should have a zero score which should be overridden)
+user/ - per-user config (keep as much in here as possible)
+        These files go into the users home directory
+
+All files in these example directory are CC0:
+To the extent possible under law, Eric Wong has waived all copyright and
+related or neighboring rights to these examples.
+
+Make targets
+------------
+
+	install-root - install system-wide files
+	               (run as root)
+	install-user - install user-specific files
+	               (run as the user public-inbox runs as)
diff --git a/sa_config/root/etc/spamassassin/public-inbox.pre b/sa_config/root/etc/spamassassin/public-inbox.pre
new file mode 100644
index 0000000000000000000000000000000000000000..161e2109469ab86bb826cdbe8846110ca557ccc1
--- /dev/null
+++ b/sa_config/root/etc/spamassassin/public-inbox.pre
@@ -0,0 +1,9 @@
+# public-inbox.org uses the Debian spamd installation + init and sets
+# CRON=1 in /etc/default/spamassassin for automatic rule updates
+
+# compile rules to C, sa-compile(1) must be run as the appropriate user
+# (debian-spamd on Debian).  sa-compile(1) will also be run by the cronjob
+loadplugin Mail::SpamAssassin::Plugin::Rule2XSBody
+
+# for ok_languages in user_prefs
+loadplugin Mail::SpamAssassin::Plugin::TextCat
diff --git a/sa_config/user/.spamassassin/user_prefs b/sa_config/user/.spamassassin/user_prefs
new file mode 100644
index 0000000000000000000000000000000000000000..9919b98ebf70a3402c01772482cff3b2fbf9a5de
--- /dev/null
+++ b/sa_config/user/.spamassassin/user_prefs
@@ -0,0 +1,26 @@
+# raise or lower as needed
+required_score 5.0
+
+# do not mess with the original message body, only notify in headers
+clear_report_template
+clear_unsafe_report_template
+report_safe 0
+
+# we do not use nor support this on NFS
+lock_method flock
+
+# do not throw off Bayes
+bayes_ignore_header X-Bogosity
+bayes_ignore_header X-Spam-Flag
+bayes_ignore_header X-Spam-Status
+bayes_ignore_header X-Spam-Report
+
+# English-only for all lists on public-inbox.org
+ok_locales en
+# we have "loadplugin Mail::SpamAssassin::Plugin::TextCat" in a *.pre file
+ok_languages en
+
+# uncomment the following for importing archives:
+# dns_available no
+# skip_rbl_checks 1
+# skip_uribl_checks 1
diff --git a/scripts/dc-dlvr b/scripts/dc-dlvr
new file mode 100755
index 0000000000000000000000000000000000000000..96009662be123cab42701d5025b424d244991831
--- /dev/null
+++ b/scripts/dc-dlvr
@@ -0,0 +1,64 @@
+#!/bin/sh
+# Copyright (C) 2008-2013, Eric Wong <e@80x24.org>
+# License: GPLv3 or later
+# to use with postfix main.cf: mailbox_command = /etc/dc-dlvr "$EXTENSION"
+DELIVER=/usr/lib/dovecot/deliver
+
+# my personal preference is to use a catchall account to avoid generating
+# backscatter, as invalid emails are usually spam
+case $USER in
+catchall) exec $DELIVER ;;
+esac
+
+# change if your spamc/spamd listens elsewhere
+spamc='spamc -U /run/spamd.sock'
+
+# allow plus addressing to train spam filters, $1 is the $EXTENSION
+# which may be "trainspam" or "trainham".  Only allow spam training
+# when $CLIENT_ADDRESS is empty (local client)
+case $1,$CLIENT_ADDRESS in
+trainspam,) exec $spamc -L spam > /dev/null 2>&1 ;;
+trainham,) exec $spamc -L ham > /dev/null 2>&1 ;;
+esac
+
+TMPMSG=$(mktemp -t dc-dlvr.orig.$USER.XXXXXX || exit 1)
+rm_list=$TMPMSG
+
+# pre-filter, for infrequently read lists which do their own spam filtering:
+if test -r ~/.dc-dlvr.pre
+then
+	set -e
+	cat > $TMPMSG
+	DEFAULT_INBOX=$(. ~/.dc-dlvr.pre)
+	if test xINBOX != x"$DEFAULT_INBOX"
+	then
+		$DELIVER -m $DEFAULT_INBOX < $TMPMSG
+		exec rm -f $rm_list
+	fi
+	PREMSG=$(mktemp -t dc-dlvr.orig.$USER.XXXXXX || exit 1)
+	rm_list="$rm_list $PREMSG"
+	set +e
+	mv -f $TMPMSG $PREMSG
+	$spamc -E --headers < $PREMSG > $TMPMSG
+else
+	$spamc -E --headers > $TMPMSG
+fi
+err=$?
+
+# normal delivery
+set -e
+
+case $err in
+1) $DELIVER -m INBOX.spam < $TMPMSG ;;
+*)
+	# users may override normal delivery and have it go elsewhere
+	if test -r ~/.dc-dlvr.rc
+	then
+		. ~/.dc-dlvr.rc
+	else
+		$DELIVER -m INBOX < $TMPMSG
+	fi
+	;;
+esac
+
+exec rm -f $rm_list
diff --git a/scripts/import_gmane_spool b/scripts/import_gmane_spool
new file mode 100755
index 0000000000000000000000000000000000000000..b5573e1574cde2e639b4a82dc9d41ffd90eda27b
--- /dev/null
+++ b/scripts/import_gmane_spool
@@ -0,0 +1,51 @@
+#!/usr/bin/perl -w
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: AGPLv3 or later (https://www.gnu.org/licenses/agpl-3.0.txt)
+#
+# One-off script to convert an slrnpull news spool from gmane
+use strict;
+use warnings;
+use Parallel::ForkManager;
+use Email::Simple;
+use PublicInbox::Filter;
+use IPC::Run qw(run);
+my $usage = "import_nntp_spool SLRNPULL_ROOT/news/foo/bar MAIN_REPO FAIL_REPO";
+my $spool = shift @ARGV or die "Usage: $usage\n";
+my $main_repo = shift @ARGV or die "Usage: $usage\n";
+my $fail_repo = shift @ARGV or die "Usage: $usage\n";
+my $nproc = `nproc 2>/dev/null` || 4;
+my $pm = Parallel::ForkManager->new($nproc);
+my @args = ('public-inbox-mda', $main_repo, $fail_repo);
+
+foreach my $n (<$spool/*>) {
+	$n =~ m{/\d+\z} or next;
+	$pm->start and next;
+	if (open my $fh, '<', $n) {
+		local $/;
+		my $s = Email::Simple->new(<$fh>);
+
+		# gmane rewrites Received headers, which increases spamminess
+		my @h = $s->header("Original-Received");
+		if (@h) {
+			$s->header_set("Received", @h);
+			$s->header_set("Original-Received");
+		}
+
+		# triggers for the SA HEADER_SPAM rule
+		foreach my $drop (qw(Approved)) { $s->header_set($drop) }
+
+		# appears to be an old gmane bug:
+		$s->header_set("connect()");
+
+		my $orig = $s->as_string;
+		close $fh or die "close failed: $!\n";
+		eval { run(\@args, \$orig) };
+		die "fail $n: $?\n" if $?;
+		die "fail $n: $@\n" if $@;
+	} else {
+		warn "Failed to open $n: $!\n";
+	}
+	$pm->finish;
+}
+
+$pm->wait_all_children;
diff --git a/scripts/report-spam b/scripts/report-spam
new file mode 100755
index 0000000000000000000000000000000000000000..825855b543d16261bd7b6e6e1e58b1cd9e957290
--- /dev/null
+++ b/scripts/report-spam
@@ -0,0 +1,28 @@
+#!/bin/sh
+# Copyright (C) 2008-2013, Eric Wong <e@80x24.org>
+# License: GPLv3 or later
+# Usage: report-spam /path/to/message/in/maildir
+# my incrontab(5) looks like this:
+#  /path/to/.maildir/cur IN_MOVED_TO /path/to/report-spam $@/$#
+#  /path/to/.maildir/.INBOX.good/cur IN_MOVED_TO /path/to/report-spam $@/$#
+#  /path/to/.maildir/.INBOX.spam/cur IN_MOVED_TO /path/to/report-spam $@/$#
+
+# gigantic emails tend not to be spam (but they suck anyways...)
+bytes=$(stat -c %s $1)
+if test $bytes -gt 512000
+then
+	exit
+fi
+
+# only tested with the /usr/sbin/sendmail which ships with postfix
+case $1 in
+*[/.]spam/cur/*) # non-new messages in spam get trained
+	exec /usr/sbin/sendmail -oem -oi $USER+trainspam < $1
+	;;
+*:2,*S*) # otherwise, seen messages only
+	case $1 in
+	*:2,*T*) exit 0 ;; # ignore trashed messages
+	esac
+	exec /usr/sbin/sendmail -oem -oi $USER+trainham < $1
+	;;
+esac
diff --git a/t/filter.t b/t/filter.t
new file mode 100644
index 0000000000000000000000000000000000000000..9c71b11f735a5bd7b6c8acd57f212ce9498edca6
--- /dev/null
+++ b/t/filter.t
@@ -0,0 +1,262 @@
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: AGPLv3 or later (https://www.gnu.org/licenses/agpl-3.0.txt)
+use strict;
+use warnings;
+use Test::More;
+use Email::MIME;
+use Email::Filter;
+use PublicInbox::Filter;
+
+sub count_body_parts {
+	my ($bodies, $part) = @_;
+	my $body = $part->body_raw;
+	$body =~ s/\A\s*//;
+	$body =~ s/\s*\z//;
+	$bodies->{$body} ||= 0;
+	$bodies->{$body}++;
+}
+
+# plain-text email is passed through unchanged
+{
+	my $s = Email::Simple->create(
+		header => [
+			From => 'a@example.com',
+			To => 'b@example.com',
+			'Content-Type' => 'text/plain',
+			Subject => 'this is a subject',
+		],
+		body => "hello world\n",
+	);
+	my $f = Email::Filter->new(data => $s->as_string);
+	is(1, PublicInbox::Filter->run($f->simple), "run was a success");
+	is($s->as_string, $f->simple->as_string, "plain email unchanged");
+}
+
+# convert single-part HTML to plain-text
+{
+	my $s = Email::Simple->create(
+		header => [
+			From => 'a@example.com',
+			To => 'b@example.com',
+			'Content-Type' => 'text/html',
+			Subject => 'HTML only badness',
+		],
+		body => "<html><body>bad body</body></html>\n",
+	);
+	my $f = Email::Filter->new(data => $s->as_string);
+	is(1, PublicInbox::Filter->run($f->simple), "run was a success");
+	unlike($f->simple->as_string, qr/<html>/, "HTML removed");
+	is("text/plain", $f->simple->header("Content-Type"),
+		"content-type changed");
+	like($f->simple->body, qr/\A\s*bad body\s*\z/, "body");
+	like($f->simple->header("X-Content-Filtered-By"),
+		qr/PublicInbox::Filter/, "XCFB header added");
+}
+
+# multipart/alternative: HTML and plain-text, keep the plain-text
+{
+	my $html_body = "<html><body>hi</body></html>";
+	my $parts = [
+		Email::MIME->create(
+			attributes => {
+				content_type => 'text/html; charset=UTF-8',
+				encoding => 'base64',
+			},
+			body => $html_body,
+		),
+		Email::MIME->create(
+			attributes => {
+				content_type => 'text/plain',
+			},
+			body=> 'hi',
+		)
+	];
+	my $email = Email::MIME->create(
+		header_str => [
+		  From => 'a@example.com',
+		  Subject => 'blah',
+		  'Content-Type' => 'multipart/alternative'
+		],
+		parts => $parts,
+	);
+	my $f = Email::Filter->new(data => $email->as_string);
+	is(1, PublicInbox::Filter->run($f->simple), "run was a success");
+	my $parsed = Email::MIME->new($f->simple->as_string);
+	is("text/plain", $parsed->header("Content-Type"));
+	is(scalar $parsed->parts, 1, "HTML part removed");
+	my %bodies;
+	$parsed->walk_parts(sub {
+		my ($part) = @_;
+		return if $part->subparts; # walk_parts already recurses
+		count_body_parts(\%bodies, $part);
+	});
+	is(scalar keys %bodies, 1, "one bodies");
+	is($bodies{"hi"}, 1, "plain text part unchanged");
+}
+
+# multi-part plain-text-only
+{
+	my $parts = [
+		Email::MIME->create(
+			attributes => { content_type => 'text/plain', },
+			body => 'hi',
+		),
+		Email::MIME->create(
+			attributes => { content_type => 'text/plain', },
+			body => 'bye',
+		)
+	];
+	my $email = Email::MIME->create(
+		header_str => [ From => 'a@example.com', Subject => 'blah' ],
+		parts => $parts,
+	);
+	my $f = Email::Filter->new(data => $email->as_string);
+	is(1, PublicInbox::Filter->run($f->simple), "run was a success");
+	my $parsed = Email::MIME->new($f->simple->as_string);
+	is(scalar $parsed->parts, 2, "still 2 parts");
+	my %bodies;
+	$parsed->walk_parts(sub {
+		my ($part) = @_;
+		return if $part->subparts; # walk_parts already recurses
+		count_body_parts(\%bodies, $part);
+	});
+	is(scalar keys %bodies, 2, "two bodies");
+	is($bodies{"bye"}, 1, "bye part exists");
+	is($bodies{"hi"}, 1, "hi part exists");
+	is($parsed->header("X-Content-Filtered-By"), undef,
+		"XCFB header unset");
+}
+
+# multi-part HTML, several HTML parts
+{
+	my $parts = [
+		Email::MIME->create(
+			attributes => {
+				content_type => 'text/html',
+				encoding => 'base64',
+			},
+			body => '<html><body>b64 body</body></html>',
+		),
+		Email::MIME->create(
+			attributes => {
+				content_type => 'text/html',
+				encoding => 'quoted-printable',
+			},
+			body => '<html><body>qp body</body></html>',
+		)
+	];
+	my $email = Email::MIME->create(
+		header_str => [ From => 'a@example.com', Subject => 'blah' ],
+		parts => $parts,
+	);
+	my $f = Email::Filter->new(data => $email->as_string);
+	is(1, PublicInbox::Filter->run($f->simple), "run was a success");
+	my $parsed = Email::MIME->new($f->simple->as_string);
+	is(scalar $parsed->parts, 2, "still 2 parts");
+	my %bodies;
+	$parsed->walk_parts(sub {
+		my ($part) = @_;
+		return if $part->subparts; # walk_parts already recurses
+		count_body_parts(\%bodies, $part);
+	});
+	is(scalar keys %bodies, 2, "two body parts");
+	is($bodies{"b64 body"}, 1, "base64 part converted");
+	is($bodies{"qp body"}, 1, "qp part converted");
+	like($parsed->header("X-Content-Filtered-By"), qr/PublicInbox::Filter/,
+	     "XCFB header added");
+}
+
+# plain-text with image attachments, kill images
+{
+	my $parts = [
+		Email::MIME->create(
+			attributes => { content_type => 'text/plain' },
+			body => 'see image',
+		),
+		Email::MIME->create(
+			attributes => {
+				content_type => 'image/jpeg',
+				filename => 'scary.jpg',
+				encoding => 'base64',
+			},
+			body => 'bad',
+		)
+	];
+	my $email = Email::MIME->create(
+		header_str => [ From => 'a@example.com', Subject => 'blah' ],
+		parts => $parts,
+	);
+	my $f = Email::Filter->new(data => $email->as_string);
+	is(1, PublicInbox::Filter->run($f->simple), "run was a success");
+	my $parsed = Email::MIME->new($f->simple->as_string);
+	is(scalar $parsed->parts, 1, "image part removed");
+	my %bodies;
+	$parsed->walk_parts(sub {
+		my ($part) = @_;
+		return if $part->subparts; # walk_parts already recurses
+		count_body_parts(\%bodies, $part);
+	});
+	is(scalar keys %bodies, 1, "one body");
+	is($bodies{'see image'}, 1, 'original body exists');
+	like($parsed->header("X-Content-Filtered-By"), qr/PublicInbox::Filter/,
+	     "XCFB header added");
+}
+
+# all bad
+{
+	my $parts = [
+		Email::MIME->create(
+			attributes => {
+				content_type => 'image/jpeg',
+				filename => 'scary.jpg',
+				encoding => 'base64',
+			},
+			body => 'bad',
+		),
+		Email::MIME->create(
+			attributes => {
+				content_type => 'text/plain',
+				filename => 'scary.exe',
+				encoding => 'base64',
+			},
+			body => 'bad',
+		),
+	];
+	my $email = Email::MIME->create(
+		header_str => [ From => 'a@example.com', Subject => 'blah' ],
+		parts => $parts,
+	);
+	my $f = Email::Filter->new(data => $email->as_string);
+	is(0, PublicInbox::Filter->run($f->simple),
+		"run signaled to stop delivery");
+	my $parsed = Email::MIME->new($f->simple->as_string);
+	is(scalar $parsed->parts, 1, "bad parts removed");
+	my %bodies;
+	$parsed->walk_parts(sub {
+		my ($part) = @_;
+		return if $part->subparts; # walk_parts already recurses
+		count_body_parts(\%bodies, $part);
+	});
+	is(scalar keys %bodies, 1, "one body");
+	is($bodies{"all attachments scrubbed by PublicInbox::Filter"}, 1,
+	   "attachment scrubber left its mark");
+	like($parsed->header("X-Content-Filtered-By"), qr/PublicInbox::Filter/,
+	     "XCFB header added");
+}
+
+{
+	my $s = Email::Simple->create(
+		header => [
+			From => 'a@example.com',
+			To => 'b@example.com',
+			'Content-Type' => 'test/pain',
+			Subject => 'this is a subject',
+		],
+		body => "hello world\n",
+	);
+	my $f = Email::Filter->new(data => $s->as_string);
+	is(0, PublicInbox::Filter->run($f->simple), "run was a failure");
+	like($f->simple->as_string, qr/scrubbed/, "scrubbed message");
+}
+
+done_testing();