When using multidrop you MUST define the Envelope-To header. Once you've
done that then your problems should go away.
How can I do this? I don't have access to the sendmail of the machine that's
keeping my mail.
What I find most strange is that I used an old version of fetchmail before and
this didn't happen, and nothing has changed on the server that keeps my
messages, so I figured I could configure fetchmail to avoid this.
I read in the FAQ that if fetchmail gets 2 consecutive identical messages it
disregards the 2nd, but in this case it's just /one/ message, and it's
fetchmail who's reproducing it.
Cheers
Aristide