Hello, been trying to fix this error all day, failed basically! Any help appreciated as I am now stuck.
We are running Exchange Server 5.5 sp4. Everything has been running perfectly for months. Recently some
users began to get an error on their Outlook 2000 clients when sending certain emails
The recipient name is not recognized
The MTS-ID of the original message is: c=US;a= ;p=Our Organisation;l=SERVER NAME-060525151211Z-21
Meantime, the NDR Report states A mail message was not sent due to a protocol error. 553 information. (#5.7.1)
This error only affects emails sent by users to .com addresses. All emails sent to .co.uk addresses and, wait for it, SOME emails sent to .com addresses are sent ok.
This problem is now escalating, instead of it being isolated users, it is now affecting many, possibly all, users. It is indeed possible that no .com emails are now being sent.
The Server (W2000 Server) that is running Exchange 5.5 is NOT the PDC. The PDC runs W2003 Server. Active Directory Connector Manager is not installed on the PDC, and never has been.
All email arrives from the Internet perfectly well.
There is no problem with our ISP Email account, I have checked.
Recent changes to the hardware/software config - absolutely nothing!
I wonder where in Exchange 5.5's zillion settings I attempt to correct this error., and I guess I don't. In fact
I think I might need a reverse DNS look up zone on the PDC. I need some help with this pliz as the fact is
emails have been working perfectly well for months until this week, and I haven't changed any settings? It
is possible we re-booted the PDC last week, and maybe it has lost some DNS settings on re-boot, really clutching at straws now...
Confusing urgent and difficult, hence maximum points!!