I understand how relay errors occur while trying to send email through one's ISP from another domain; however this seems to be coming from our own Exchanger Server 2003.
I had this error a couple of weeks ago to a different domain, again, it appeared out of the blue after having sent emails to that domain. I added all internal IPs to the allowed relay and that seemed to fix it.
So far, only one employee and myself are having the problem. There only maybe three employees who would have cause to contact this client. When this happened before, it was a vendor that only two employees needed to email and myself.
Authentication types are:
The permissions for Windows Integrated are set to "Authenticated Users".
I have an SMTP virtual server on another server which processes spam. It is only set to Anonymous.
I have sent test emails this morning, but have not received delivery receipts or NDRs.
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