We had a problem earlier today with an IMail list server at AMBIENCE.COM.AU
looping mail back to LISTSERV (kind of like majordomo used to have a
tendency to do), and just a few minutes ago a customer wrote in saying
she was having the same problem with the same host.  If this happens
to you you can stop the loop by adding

[log in to unmask]
[log in to unmask]

(or whatever variation for your specific platform--and under unix don't
forget to export) followed by a restart of the server.  This will stop
LISTSERV from responding to imailsrv and will break the loop.

It might be reasonable to add this as imailsrv@* but I'm not sure if
this is the default administrative account for an IMail list server.

Nathan