Non-standard message-id format

https://github.com/apache/incubator-ponymail-foal/blob/b4c6d4cca3d03a48739766b2a758dc4fb025e076/server/endpoints/compose.py#L78

A message id normally ends with @domain-identifier, where the domain is the sender domain.
This is done to reduce the chance of clashes with ids for other domains.

AFAICT the above id uses the destination domain, which is not generally under the sender's contol.

https://en.wikipedia.org/wiki/Message-ID

Start at server/endpoints/compose.py around line 78 and compare the generated Message-ID with the linked Message-ID guidance. Verify that the identifier uses the sender's domain rather than the destination domain, and confirm that the resulting format is covered by any existing compose-related checks.

Written by the indexing model from the issue text.