Recipient is blacklisted so mail won't send

NewCow

I have Dockerized Mailcow up and running. I am sending an email to a known address @centurytel.net. When I hit send, I get a popup message that the recipient’s IP address is on a blacklist and the mail will not be sent. Is there a whitelist for this and can I add the IP address, or must it be the domain? Thank you in advance for all assistance!!

Mailerinoo

Have you already checked your Fail2Ban settings in the admin panel? Potentially the IP address is blocked there?

NewCow

Only one entry there, 141.0.0.0/8, thanks for the suggestion.

Maybe I should clarify. This is a brand new install, so virtually all the whitelists/blacklists are empty. The problem is that the IP of the recipient of the outgoing email is blacklisted by zen.spamhaus.org. Thank you.

D4niel

NewCow Only one entry there, 141.0.0.0/8, thanks for the suggestion.

Are you sure that you want to ban 16 million potential mail severs?

NewCow

Hmm, or could it be Thunderbird?

NewCow

Ah, wrong port number for SMTP in Thunderbird. I changed it from 25 to 587 and now mail sends. Sorry to bother everybody.

NewCow

D4niel Hmm, a little heavy handed perhaps. Thanks for the heads up!