That's what I've found in my mail archive:Fixed: Messages with Footers Sent Multiple TimesPreviously, when the IronPort appliance added a footer to an outgoing HTML message, the message may be sent to the recipient multiple times. This occurred becau...

I'm pretty sure that this was the faulty version....

I saw this behaviour several times in the last year. As far as I remember there was a bug in the AsyncOS. Do you have the latest release on your system? Regards,Joerg

What about a second listener for domain2.com? You can disable bounce verificatin for all incoming mails on that listener.

If you have an Exchange 2007 server you have also at least one domain controller (DC). Use LDAP and validate addresses against the active directory.