External email to mailbox alias being rejected with 554 5.7.1 recipient address rejected.

Question

We have a single on premise Exchange 2016 server. We've added an extra email address to one of our user's mailboxes using the EAC. We are able to email that alias internally, but no one outside of our organization can email that address. The bounce message that the sender gets is "Message Blocked 554 5.7.1 <email address alias> Recipient address rejected: Access Denied." I've looked at the mailbox configuration and the message tracking log and can't find anything wrong. How do I find what is causing the the email to be rejected? Thanks.

Answer 1

Hi Mike Morgan,

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“We discovered the problem. We have recently performed an administrator password change in active directory. That caused a sync operation interruption with Sophos Central (our email protection solution). Once the password was changed on the agent, AD began syncing again and external email is now being received. Thank you for your help.”_  

Glad to see that your issue had already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer.  

[External email to mailbox alias being rejected with 554 5.7.1 recipient address rejected.]  

Issue Symptom:

We are able to email that alias internally, but no one outside of our organization can email that address.  

Solution:

Once the password was changed on the agent, AD began syncing again and external email is now being received.  

Best Regards,

Jarvis Sun

Answer 2

Could you check what FQDN is defined on their SEND connector?

Ideally, it should be such as mail.domain.com.

Check your barracuda advanced filtering settings for something similar to - "Validate helo/ehlo" check box.

Answer 3

We discovered the problem. We have recently performed an administrator password change in active directory. That caused a sync operation interruption with Sophos Central (our email protection solution). Once the password was changed on the agent, AD began syncing again and external email is now being received. Thank you for your help.