Why do I keep getting a 554 5.7.1: Relay access denied?
Sentinel Messaging is a closed relay system. This means that all mail going through the Sentinel Messaging platform must have a user associated with the platform, whether that be End-User, alias, or Functional Account.
To resolve this issue you will want to check a few areas on the platform.
Check to see if the Domain has relay access turned on.
Go to Company Settings -> Domains then make sure the switch is turned on to green.
Check the Users and Groups
Make sure the user who is getting the relay access denied message is listed in this section.
If the account is a functional account, make sure the account is also listed under Functional Accounts tab.
Note* If you just added the user in the last hour or enabled relay on the domain, your changes might have not taken effect. Give any enabled domain or added user 30 to 60 minutes to properly propagate on the platform.
If you still keep getting this error message after trying these steps please contact support.