Mail server (Debian/Postfix/Dovecot) and rejected emails

Question

I have a mail server running Debian Lenny with Postfix and Dovecot. I send and receive emails without any problems with most of my contacts using Google Mail or Yahoo Mail but some of my contacts will not get my emails.

I do receive a undelivered mail report saying: "xxxxxxxxxx@skybest.com: Recipient address rejected: "DOBLOCK residential dynamic ip space with zombie activity" (in reply to RCPT TO command)"

I am able to send these contacts emails using Google Mail so I assume the problem is with my server setup. What exactly is wrong with my setup? How can I fix it?

Thanks for your help.

Answer 1

There is probably nothing wrong with your server - it's simply connected to the internet through a network that is considered untrostworthy by others.

Most of the time, this is because the IP of your server is listed in one of the many DNS blacklists out there, for example DSBL or zen.spamhaus.org. For dialup connection, this is pretty normal and there is nothing you can do (except using your ISPs mailserver, the one you'd use in Outlook/Thunderbird, as a relay for outgoing mail).

If that's a rented server, you should really talk to their tech support and have them undergo the steps necessary to get their IP space off any blacklists.

Answer 2

There might actually be nothing wrong with your setup. Except that you are trying to send mails from a dynamically allocated IP address e.g. with a dialup account. Many MTAs (mail servers) reject mails from a client from within an IP range which is used for dialup accounts because most spam mails today are probably delivered by compromised consumer computers.

Answer 3

Thanks a lot for your answers. You both were right saying that the problem didn't come from my setup but from my IP. I have a static IP and I am not backlisted as a spammer or anything. The problem seems to be (at least for AOL but it might be the same with skybest) that a reverse DNS query doesn't return my domain name, instead it shows the name of my ISP (free.fr in France). Luckily my ISP does offer to customize a reverseDNS for a given IP so it might be possible for me to overcome the problem.Thanks again