Why does 550 5.7.1 Unable to relay occur?

Question

Domain Name System

When sending letters via outlook to the world (External addresses), the system gives an error 550 5.7.1 Unable to relay. If you send via webapps there is no problem. Outlook is configured via IMAP. Whose side is the problem on?

Answer 1

The problem is not in the IMAP settings, but in the SMTP settings. Most likely, you forgot to enable authorization for SMTP.