If you want to fix up messages with blank Message-ID: fields you can add
something like the following to your LMTP transport:
headers_remove = ${if match{$h_Message-ID:}{\N^\s*$\N} \
{Message-ID} {} }
Tony.
--
<fanf@???> <dot@???>
http://dotat.at/ ${sg{\N${sg{\
N\}{([^N]*)(.)(.)(.*)}{\$1\$3\$2\$1\$3\n\$2\$3\$4\$3\n\$3\$2\$4}}\
\N}{([^N]*)(.)(.)(.*)}{\$1\$3\$2\$1\$3\n\$2\$3\$4\$3\n\$3\$2\$4}}