Andy Still waiting for the version jengelh said has 'backfill_transport_headers' fix (gromox-2.20-125-geb8871984)
The Gromox smtp error:-
[2024-01-04 16:29:42.870612]: *** config key "context_num" has no default and was not set either; yielding 0
Adding the line below to /etc/gromox/smtp.cfg
context_num=400
prevents this error in the log file. This was reported by another user on the forum some weeks ago but I can't remember/find which one sorry.