Greetings everyone,

Not so much a question but something I found the other day. Some background...

Up until about a week ago postfix was running fine on our public web / mail server. Then after that it stopped processing incoming mail. Outgoing mail went out fine but whenever I'd send a test message through Gmail or elsewhere, my mail would just get 'stuck' and never process. Other senders said they got a bounce message but I personally never received one -- my message just got lost to the ether.

After some troubleshooting, I found that the following line in /etc/postfix/main.cf was causing the problem:

When I removed the reject_rbl_client entries from the end of this config line, everything went back to normal and mail is now processed near-instantaneously. Yes, I realize that my system can no longer check the third-party blacklists, but that's a low priority compared to actually receiving business emails!

I'm posting this message in case anyone in the future has a similar issue. If you temporarily remove these two third-party blacklists you can test if they are causing the issue. I personally think it's a bad idea for postfix to include third-party blacklists in the default install without some sort of automated mechanism to skip them if they are acting up as they were/are for me. Since postfix doesn't have a semi-modern way to interact with them (for bug verifying / reporting, etc) I haven't bothered to contact them -- "Posts from non-members will be silently deleted" -- not a very inviting attitude...

Thanks!

Where did you get your "default install" from?
I don't recall any of that in a fresh main.cf - you're supposed to configure it to your own requirements.

Hi descendant_command!

You know, that's a good question. I thought it came directly from postfix (I did a `grep -r spamhaus *` command and had lots of hits on the postfix's source code) but I'm not actually seeing it in the original main.cf included in the source. It's possible my VPS provider did this? At any rate, I didn't do this myself and momentarily thought this was part of an Ubuntu patch, but I'm not seeing any Ubuntu code touching main.cf. Weird. I stand corrected -- this *isn't* part of the default install then, not from Ubuntu or postfix anyway...

Still, a cautionary tale to those who may encounter a similar issue.

Free services tend to disappear over time as they gain popularity and decide to monetise this, usually for their new owners...
I've seen a few RBL's go AWOL over the years.
Well worth being aware of what external services your kit is relying on.