sorry if this is a duplicate question. I was looking through similar questions but wasn't able to find anything helpful.
One user and only one user is getting an error message back when they try to send mail to an external address. Another user sends the same email to the same address and succeeds. Here is the error message:
From: Microsoft Outlook Sent: Tuesday, June 12, 2018 1:30 PM To: Username Subject: Undeliverable: Subject
exchangeserver.domain.com rejected your message to the following e-mail addresses:
name@extdomain.com (name@extdomain.com)
exchangeserver.domain.com gave this error: Unable to relay
Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept e-mail from certain senders, or another restriction may be preventing delivery.
Diagnostic information for administrators:
Generating server: exchangeserver.domain.com
name@extdomain.com
exchangeserver.domain.com #550 5.7.1 Unable to relay ##
The weird thing is, the user account that is getting blocked is a copy of the account that succeeded.
I've already verified that the "Require that all senders are authenticated" box is unchecked in EMC.
Exchange 2010 is running on a 2008 R2 server.
I am fairly new to Exchange and I am not really sure where to go from here.
If the question lacks detail please let me know what I can add to help clarify.
Update1: The user was not able to send mail to the same email via OWA either. However, they are able to send mail to their personal (non-company) email address.