lib/PublicInbox/LeiToMail.pm | 10 +++++++---
 lib/PublicInbox/NetReader.pm |  8 +++++++-

diff --git a/lib/PublicInbox/LeiToMail.pm b/lib/PublicInbox/LeiToMail.pm
index 2aa3977e8034d01f744c05a3a7c5598c9e97890e..03cbde3bd7cf264c141f885a8b4e73c157b30865 100644
--- a/lib/PublicInbox/LeiToMail.pm
+++ b/lib/PublicInbox/LeiToMail.pm
@@ -310,8 +310,11 @@ 	my ($self, $lei) = @_;
 	my $dedupe = $lei->{dedupe};
 	$dedupe->prepare_dedupe if $dedupe;
 	my $append = $lei->{net}->can('imap_append');
-	my $uri = $self->{uri};
-	my $mic = $lei->{net}->mic_get($uri);
+	my $uri = $self->{uri} // die 'BUG: no {uri}';
+	my $mic = $lei->{net}->mic_get($uri) // die <<EOM;
+E: $uri connection failed.
+E: Consider using `--jobs ,1' to limit IMAP connections
+EOM
 	my $folder = $uri->mailbox;
 	$uri->uidvalidity($mic->uidvalidity($folder));
 	my $lse = $lei->{lse}; # may be undef
@@ -749,7 +752,8 @@ 	if ($au_peers) { # wait for peer l2m to finish augmenting:
 		$au_peers->[1] = undef;
 		sysread($au_peers->[0], my $barrier1, 1);
 	}
-	$self->{wcb} = $self->write_cb($lei);
+	eval { $self->{wcb} = $self->write_cb($lei) };
+	$lei->fail($@) if $@;
 	if ($au_peers) { # wait for peer l2m to set write_cb
 		$au_peers->[3] = undef;
 		sysread($au_peers->[2], my $barrier2, 1);
diff --git a/lib/PublicInbox/NetReader.pm b/lib/PublicInbox/NetReader.pm
index c1af03a3f8b972db9a8ff38f0b081652dbb90a53..4de2583e00ddeb307aea560da2b9070e3dadf99c 100644
--- a/lib/PublicInbox/NetReader.pm
+++ b/lib/PublicInbox/NetReader.pm
@@ -685,7 +685,13 @@ 		}
 	}
 	my $mic = mic_new($self, $mic_arg, $sec, $uri);
 	$cached //= {}; # invalid placeholder if no cache enabled
-	$mic && $mic->IsConnected ? ($cached->{$sec} = $mic) : undef;
+	if ($mic && $mic->IsConnected) {
+		$cached->{$sec} = $mic;
+	} else {
+		warn 'IMAP LastError: ',$mic->LastError, "\n" if $mic;
+		warn "IMAP errno: $!\n" if $!;
+		undef;
+	}
 }
 
 sub imap_each {