Hi all, We had a mail-storm because of a loop generated by a user who has set up a rule in OWA, which automatically forward all incoming mail to an external address, which, however, generated an NDR. It is possible to avoid mail loop in Exchange 2003 in some way? Andrea

Yes, do not allow auto-replies / auto-forwards to the Internet. It's disabled by default for these very reasons: http://support.microsoft.com/kb/266166