[Mailman-Users] -owner and -request not working on new host

[Nina Nicholson]

I recently moved my site from a host that provided Mailman 2.1.5 and Plesk
8.1 to one that provides Mailman 2.1.9 and Plesk 10.1.1.

I manually created 55 lists on the new host through Plesk, and populated
them in the Mailman admin. All of them have the same two emails in the
-owner field, which were also the same ones used for the old lists on the
old host.

My problem is that emails sent to both the -owner and -request addresses
bounce back with the message that that address doesn't exist.

Interestingly I tried to manually created -owner and -request addresses for
one of the lists (news at domain.org) via Plesk, and was prevented with the
message that news-owner at domain.org and news-request at domain.org were already
in use. So Plesk thinks they exist -- but trying to send anything to them
fails.

I am not a Linux guru. How do I go about debugging this?