[Mailman-Users] mailman unsubscribes list-admins

[einsnull admin]

hi, i do have 2 little problems, maybe someone could help me:

1. i often have error messages like this in my logs/smtp-failure:

Oct xxx 2003 (189) delivery to mail at virtual-domain.com failed with code 
553: 5.3.0 <mailman-bounces at virtual-domain.com>... User unknown

where mail at virtual-domain.com is the address of the administrator of that 
list. maybe this is the reason for the 2nd problem:

2. periodically, the administrators of some lists are unsubscribed 
automatically because of bounces. but the admin-addresses are reachable.

of course, the address mailman-bounces at virtual-domain.com does not exist 
as we installed only one mailman-list with the main domain of our server. 
there only exists an address like list-name-bounces at virtual-domain.com

does anyone has a hint?

thanks,
u.