We have 3 exchange 5.5 SP 4 servers located in 3 different sites connected with site connectors not x.400, all 3 sites have Windows 2000 AD. The internet mail connector is located at head office. All 3 sites are connected via VPN.
Here is my issue; when a user at a site sends an email with both an external and internal email address with an attachment, they receive a bounce back only for the user at head office. The email will reach the external address and the other site. If they send the same email and remove the attachment everyone receives the email. Here is the error the sender receives (italics have been changed). There are plans for an upgrade to Exchange 2003.
head office user on 2011-02-04 11:37
Unable to deliver the message due to a communications failure
The MTS-ID of the original message is: c=US;a= ;p=location;l=server-110204183315Z-314
MSEXCH:MSExchangeMTA:location:head office server
I have looked at solutions on EE and the majority point to DNS but I don't think it's a DNS issue because without the attachment everyone receives the email.
Any help would be appreciated.
Thanks in advance,