1 files changed, 4 insertions, 0 deletions
diff --git a/lib/PublicInbox/Filter.pm b/lib/PublicInbox/Filter.pm
index a1587682..e784cded 100644
--- a/lib/PublicInbox/Filter.pm
+++ b/lib/PublicInbox/Filter.pm
@@ -201,6 +201,10 @@ sub collapse {
          my ($mime, $part) = @_;
          $mime->header_set('Content-Type', $part->content_type);
          $mime->body_set($part->body_raw);
+        my $cte = $part->header('Content-Transfer-Encoding');
+        if (defined($cte) && length($cte)) {
+                $mime->header_set('Content-Transfer-Encoding', $cte);
+        }
          mark_changed($mime);
          return 1;
  }