why does forwarding to an external email address with procmail not work?

Question

I am using the following recipe in my .procmailrc file to forward a copy of all email messages to another account:

:0 c
! somebodyelse

This works fine. But if I try to use forward to an external email address:

:0 c
! somebodyelse@example.com

It does not work. Procmail seems to send the mail fine, postfix (on the same computer) then forwards it to an smtp smart host which apparently accepts it without errors, but it never arrives.

Any idea?

Answer 1

You already got the answer. The smart host accepts the mail. It is now in charge of delivering as defined in RFC 5321. If it doesn't then contact the smart host admins and complain. They are the culprit not following the rules.