Why does Mailman show errors about an "implicit destination"?

Sometimes, messages sent to a Mailman list may be held until the moderator approves them, with the reason being that the “Message has implicit destination”.

This means that the message was forwarded or BCC:ed to the list’s address, instead of being sent directly to the list in the “To:” or “CC:”.

It’s generally considered dangerous to accept these kinds of messages; it sometimes leads to mistakes, and confuses filtering systems some people use that look for the list address in the message headers. Because of that, the Mailman default is to require that the original sender make their intention “explicit” by including the list’s real address in the “To:” or “CC:” address of a mail program.

However, if you really want Mailman to accept an “implicit” destination address, you can do that:

  1. Login to the Mailman list management pages.
  2. Click Privacy options, then Recipient filters.
  3. Change the “Must posts have list named in destination (to, cc) field (or be among the acceptable alias names, specified below)” option from “Yes” to No.