Index: a/frontends/mailpost.in
===================================================================
--- a/frontends/mailpost.in	(revision 10164)
+++ a/frontends/mailpost.in	(revision 10165)
@@ -217,4 +217,9 @@
     next if /^Approved:\s/sio && defined($approved);
     next if /^Distribution:\s/sio && defined($distribution);
+
+    # Remove empty header lines within header body.
+    s/\n[ \t]+\n/\n/g;          # middle lines in header field
+    s/\n[ \t]+$//;              # last line in header field
+    s/^([^:]+:[ \t]+)\n/$1/;    # first line in header field
 
     # Collect empty header field names.
