Mailman list emails discarded as duplicate

[Leon Baker]

Hi,

I'm having an issue archiving Mailman list emails. I have two users of 
the archive that are both subscribed to the same Mailman list. The first 
user gets all the list emails but the list emails for the second user 
are discarded as duplicates. As the second users email address does not 
appear anywhere in the stored list email (and shouldn't), he has no way 
of seeing it in the archive.

Mailman is setting the To header of both emails to the users own email 
address. Even though the To headers are different, the second email is 
discarded.

How does the duplicate checking work? Are any other headers compared 
besides the Message-ID? I tried setting extra_to_field=X-Original-To: as 
the header is present but this didn't help.

Regards,
Leon