[Mailman-Users] problems with mail robot -request

[Joe]

Dear Mailman-Users and Team,

i am using mailman for a long time now and like for once to say thanks 
for the good work!

  A while ago we migrated the server and the lists. It comes that i 
recognized a problem. A mail to the mail robot 
mylist-request at mylist.domain goes straight to the moderation-queue and 
the user got a bounce that the mail is held for approval. Even when the 
moderator approves the mail - it is published to the list and not to the 
mail-robot.

My first idea was that the migrated lists are buggy - but the same 
behaviour occurs after creating a new list.

We are using virtualhosts and postfix as a mta.

Any Ideas howto debug or which steps to take to get this problem solved 
are highly appreciated?

  Joe