lib/PublicInbox/LeiExportKw.pm | 12 +++++++++++-
 lib/PublicInbox/NetWriter.pm   |  9 +++++++++
 t/lei-export-kw.t              |  2 +-
 t/lei-import-imap.t            |  3 +++

diff --git a/lib/PublicInbox/LeiExportKw.pm b/lib/PublicInbox/LeiExportKw.pm
index 756d0e9c0a4d0d5831ad761cd046ea041394e37b..0ecfb7829772b68875c579c6c9901ba1d34b2610 100644
--- a/lib/PublicInbox/LeiExportKw.pm
+++ b/lib/PublicInbox/LeiExportKw.pm
@@ -67,7 +67,17 @@ 		require PublicInbox::LeiToMail; # kw2suffix
 		$self->{lms}->each_src($input, \&export_kw_md, $self, $mdir);
 	} elsif ($input =~ m!\Aimaps?://!i) {
 		my $uri = PublicInbox::URIimap->new($input);
-		if (my $mic = $self->{nwr}->mic_for_folder($uri)) {
+		my $mic = $self->{nwr}->mic_for_folder($uri);
+		if ($mic && !$self->{nwr}->can_store_flags($mic)) {
+			my $m = "$input does not support PERMANENTFLAGS";
+			if (defined $self->{lei}->{opt}->{all}) {
+				$self->{lei}->qerr("# $m");
+			} else { # set error code if user explicitly requested
+				$self->{lei}->child_error(0, "E: $m");
+			}
+			return;
+		}
+		if ($mic) {
 			$self->{lms}->each_src($$uri, \&export_kw_imap,
 						$self, $mic);
 			$mic->expunge;
diff --git a/lib/PublicInbox/NetWriter.pm b/lib/PublicInbox/NetWriter.pm
index 629a752ae79a3b3b1c1ea8ed91e029f925801268..4a1f34f63c458a5733d58569c8b0c6a945678adf 100644
--- a/lib/PublicInbox/NetWriter.pm
+++ b/lib/PublicInbox/NetWriter.pm
@@ -56,4 +56,13 @@ 	$mic->store($uid, 'FLAGS.SILENT', '('.kw2flags($kw).')');
 	$mic; # caller must ->expunge
 }
 
+sub can_store_flags {
+	my ($self, $mic) = @_;
+	for ($mic->Results) {
+		/^\* OK \[PERMANENTFLAGS \(([^\)]*)\)\].*/ and
+			return $self->can('perm_fl_ok')->($1);
+	}
+	undef;
+}
+
 1;
diff --git a/t/lei-export-kw.t b/t/lei-export-kw.t
index 55730e87c050c45e167b9edda3c92da44929264c..88b2a80b9904c222dde88a130baa79bfbcbae989 100644
--- a/t/lei-export-kw.t
+++ b/t/lei-export-kw.t
@@ -4,7 +4,7 @@ # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict; use v5.10.1; use PublicInbox::TestCommon;
 use File::Copy qw(cp);
 use File::Path qw(make_path);
-require_mods(qw(lei -imapd Mail::IMAPClient));
+require_mods(qw(lei)); # see lei-import-imap.t for IMAP tests
 my ($tmpdir, $for_destroy) = tmpdir;
 my $expect = eml_load('t/data/0001.patch');
 my $do_export_kw = 1;
diff --git a/t/lei-import-imap.t b/t/lei-import-imap.t
index 315567b3b8d4fea66bd2211e11cf377aaee603ea..3b6cb29926eee322355365631ff636c3d261eb3b 100644
--- a/t/lei-import-imap.t
+++ b/t/lei-import-imap.t
@@ -110,6 +110,9 @@ 	$out = json_utf8->decode($lei_out);
 	is(scalar(@$out), 2, 'got JSON') or diag explain($out);
 	lei_ok qw(lcat), $url_orig;
 	is($lei_out, $orig, 'lcat w/o UID works');
+
+	ok(!lei(qw(export-kw), $url_orig), 'export-kw fails on read-only IMAP');
+	like($lei_err, qr/does not support/, 'error noted in failure');
 });
 
 done_testing;