Requested action not taken: mailbox unavailable
Server replied: 550 Verification failed for <user@domain.com>
Connection rejected: SPAM source domain.com is manually blacklisted.
Sender verify failed
This is usually caused by the domain name you are sending from is in the list of blocked domains. To fix it, ssh in to the server and edit:
vim /etc/blockeddomains
remove the domain name from that file and save it. I don’t believe you need to restart anything, but just in case try restarting exim as well:
service exim restart
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.