I receive a 550, 553, or relay-prohibited error when sending email ...
Symptom. When you're away from home and send an email message using your home email account, your email message might be returned with a 550, 553, or relay-prohibited error message. The same situation could occur when you're away from your office and try to send an email message using your work email account.
Applies To:
Outlook for Microsoft 365, Outlook 2021, Outlook 2019, Outlook 2016, Outlook 2013