lib/PublicInbox/Import.pm       |  2 +-
 lib/PublicInbox/V2Writable.pm   |  2 +-
 lib/PublicInbox/WatchMaildir.pm | 21 ++++++++++++++++++++-

diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index ae508cd80132ed496fe2ed1c627df7e3246e7d66..fb813159ef779bfc1eb06d24d6e76f570bea2e4b 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -387,7 +387,7 @@ 	drop_unwanted_headers($mime);
 
 	# spam check:
 	if ($check_cb) {
-		$mime = $check_cb->($mime) or return;
+		$mime = $check_cb->($mime, $self->{-inbox}) or return;
 	}
 
 	my $blob = $self->{mark}++;
diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index 8b31b69a62f7fb01f8525ae997c9bc05c74330bf..528f5e9a5650df2866b60e5ad602306a8c0eda37 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -171,7 +171,7 @@ 	my ($self, $mime, $check_cb) = @_;
 
 	# spam check:
 	if ($check_cb) {
-		$mime = $check_cb->($mime) or return;
+		$mime = $check_cb->($mime, $self->{-inbox}) or return;
 	}
 
 	# All pipes (> $^F) known to Perl 5.6+ have FD_CLOEXEC set,
diff --git a/lib/PublicInbox/WatchMaildir.pm b/lib/PublicInbox/WatchMaildir.pm
index efc9849a6effa694b33909179a7cc7f4de71ac40..ec28a3034ff84962b034ea53fa27ede943e251a9 100644
--- a/lib/PublicInbox/WatchMaildir.pm
+++ b/lib/PublicInbox/WatchMaildir.pm
@@ -12,6 +12,8 @@ use PublicInbox::Filter::Base qw(REJECT);
 use PublicInbox::Spamcheck;
 use PublicInbox::Sigfd;
 use PublicInbox::DS qw(now);
+use PublicInbox::MID qw(mids);
+use PublicInbox::ContentHash qw(content_hash);
 use POSIX qw(_exit);
 *mime_from_path = \&PublicInbox::InboxWritable::mime_from_path;
 
@@ -988,10 +990,27 @@
 	$importers->{"$ibx"} = $im;
 }
 
+# XXX consider sharing with V2Writable, this only requires read-only access
+sub content_exists ($$) {
+	my ($ibx, $eml) = @_;
+	my $over = $ibx->over or return;
+	my $mids = mids($eml);
+	my $chash = content_hash($eml);
+	my ($id, $prev);
+	for my $mid (@$mids) {
+		while (my $smsg = $over->next_by_mid($mid, \$id, \$prev)) {
+			my $cmp = $ibx->smsg_eml($smsg) or return;
+			return 1 if $chash eq content_hash($cmp);
+		}
+	}
+	undef;
+}
+
 sub _spamcheck_cb {
 	my ($sc) = @_;
 	sub {
-		my ($mime) = @_;
+		my ($mime, $ibx) = @_;
+		return if content_exists($ibx, $mime);
 		my $tmp = '';
 		if ($sc->spamcheck($mime, \$tmp)) {
 			return PublicInbox::Eml->new(\$tmp);