Hello Ron, 
Are you seeing any errors in the delivery logs? This should point to why the message was not forwarded. Thank you

Tony, thank you for the reply.  So here is our error:

[2022.09.28] 19:48:50.610 [36842549] Delivery for mailadmin@mydomain.com to xxxxxx@gmail.com has bounced. Reason: Remote host said: 550 Outbound SMTP is not allowed

The alias has "Include All Domain Users" checked.

Hi Ron, 

If mailadmin@mydomain.com is a user mailbox, please edit the account and check their Service Access card to ensure Outgoing SMTP is enabled. 

If mailadmin@mydomain.com is the alias address, you may also need to enable the setting for "Alias can be used as from address in webmail". This setting is required in order to use an alias address as the From address of an email. Please try that and see if it allows the email to be delivered.

Hello Ron, 

Adding to Andreas response, can you also show the "Display Related Traffic" results. This can show other errors as well, something like

password has expired ( for example ) 

Thank you

Actually Tony you are right.  We found

[2022.11.04] 10:43:33.046 [42284025] Outbound SMTP is not allowed. Reason: Password expired.

Glad to hear you were able to find the issue Ron.