On Mon, Jan 19, 2026 at 08:00:32AM +0100, Jan Eden wrote: > > This should have resulted in a similar error message as before, since > the expansion of the list address (testing) does not exist as a local > user. Instead, I get this error message: > > -------------------------------------------------- > msmtp: recipient address [email protected] not accepted by the server > msmtp: server message: 524 5.2.4 Mailing list expansion problem: > <[email protected]> > -------------------------------------------------- > > This does not make any sense to me – how does OpenSMTPD know that > [email protected] is a mailing list? > > - Jan >
“Mailing list expansion problem” is a generic error message when an address fails to match in a “virtual” I think. I’ve had this error message without working with mailing lists. >From what I can remember, my issue was that my virtual alias table had mappings from, e.g. [email protected] to [email protected] but OpenSMTPD also needs a final mapping from [email protected] to a local user (which, in my case, is used for lmtp delivery, while using the last matched address as rcpt-to). Maybe enabling tracing and debug logs with smtpctl could help you understand your issue.
