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Title
Testing email in Alarm Action gave "Sending email failed : unknown Email address amongst these addresses ; error is 550 5.7.1 Unable to relay" -
Description
When testing an email for an alarm action, this error is thrown:"Sending email failed : unknown Email address amongst these addresses ; error is 550 5.7.1 Unable to relay" -
Cause
Caused by authentication issue with mail server.https://social.technet.microsoft.com/Forums/en-US/1a84a06a-f1c8-40b4-ace8-1e264f218aa1/550-571-unable-to-relay-for?forum=exchangesvrsecuremessaginglegacyhttps://support.microsoft.com/en-us/kb/2773786 -
Resolution
The error is being sent back from the mail server. Please ask the Mail Server Admin to see if the email in question is being held up on the mail server end?