This Knowledge Base article was written specifically for the Atlassian Server platform. Due to the Restricted Functions in Cloud Applications the contents of this article cannot be applied to Atlassian Cloud applications.
Outlook cannot handle outbound mail. One or more of the following appears in the
There is a known bug tracked in JRA-31238 - Exchange with authentication requires From address matches the authenticated user Verified which has been verified to affect instances where the project level From address is configured to be different from the global SMTP From address in JIRA.
Your Exchange mail server is not configured to relay messages.