luchris I have a user who is trying to send out an email. But it was caught by barracudacentral.org. Is there a way to make postfix not to lookup authenticated sender? Thank you. Sending of the message failed. An error occurred while sending mail. The mail server responded: Service unavailable; Client host [116.14.85.230] blocked using b.barracudacentral.org; http://www.barracudanetworks.com/reputation/?pr=1&ip=116.14.85.230. Please check the message recipient “test@email.com” and try again.
esackbauer Who is that server 116.14.85.230? Obviously that is not a mailcow instance. Is the user trying to send to mailcow, or send from mailcow? That IP is flagged as dynamic IP and has “vpn.dnhybrid.com” as hostname, please clarify how this can be.
luchris Hi, This IP is the user’s internet IP. The user is trying to send out an email to test@email.com (masked email address). The IP was caught by their own mailcow server and refuse to deliver the email. It is their static IP address with that rDNS It is their static IP address with that rDNS
esackbauer The problem is with the user, not your mailcow. His mail server is running on that IP, and this IP is on several blacklists. https://mxtoolbox.com/SuperTool.aspx?action=blacklist%3a116.14.85.230&run=toolpage
luchris esackbauer No, it isn’t. That vpn.dnhybrid.com is their internet IP, and mailcow has rejected accepting the user email because the user’s IP vpn.dnhybrid.com is listed at barracuda.
esackbauer If that IP is not changing, and you want to allow to send from this IP, you can add this IP to the “forwarding hosts” in Mailcows admin UI. But then everyone at that IP could abuse your mailcow and send spam from that IP. If you are trusting that IP address its OK. Better solution would be that user gets a mailcow mailbox and does send authenticated via port 587
esackbauer RBL is only checked if you are sending via Port 25. If the user sends via Port 587 and is authenticated, no RBL check happens. Users should never send via port 25. https://docs.mailcow.email/client/client-manual/