Message not sent.
Requested action not taken: mailbox unavailable
Server replied: 550 Verification failed for <user@domain.com>
The mail server could not deliver mail to user@domain.com. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries.
Sender verify failed
If you get this error on a server with cpanel, it might mean the mail for the domain is set to Remote but should be local.
To fix it from cpanel, go into the “MX Entry” option (if it’s there) and switch it from Remote/Local.
From WHM you can go to WHM >> DNS Functions >> Edit MX Entry then change it from Remote/Local there.
Also on both of those, I would recommend making sure the MX entries below are set correctly as well, these should be pointed to whatever mailserver your domain is supposed to use for mail.
If you are getting other “Server replied: 550 Verification failed for” errors, try these links possibly if your error matches:
Connection rejected: SPAM source domain.com is manually blacklisted.
No Such User Here
The mail server could not deliver mail to user@domain.com. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries.