Forum messages are no longer delivered to my mailbox

Meta Help!
1

We’re sorry, but we’re having trouble reaching you via email. Our last few emails to you have all bounced back as undeliverable.

Who do I contact about this? I replied to the most recent message regarding undelivered messages 3 days ago. No response.

I previously received messages from these groups. Then they stopped arriving and these “undeliverable message” messages accumulated in my account. Nary a response to any replies. I do not receive any messages, accepted or rejected; they never arrive at our server.

Is there anyone here capable of reading pixls’ mail server logs to discover the issue?

2

@paperdigits ?

3

@jimoe who is hosting your email? We have too many bounces from your email provider, and when that happens too many times the system stops trying to send email. This has apparently been happening for two years for you.

4

I finally found the problem: The messages got caught in our spam filters and the IP (65.108.31.59) was blocked at the firewall.

At the moment I do not understand why the messages were considered spammy. One filter looks for multiple failed logins; another tests for extortion phrases. Neither of which I would expect from Pixls.

I will study this more closely.

5

If you are interested, here is what happened.

Our spam filter has a whitelist, and uses a feature called “greylisting.” The feature looks for the sender in a whitelist; if not found it responds with a “temporarily unavailable, try again later” message, and adds the IP to the greylist. When the sender re-sends the message, it is found in the greylist and processes the message.

Greylisting is very effective against “fire-and-forget” spam. It represents about 60% of the rejected messages.

Some unique features of pixls’ mail server caused a failure of the greylist and whitelist functions.

  1. The spam filter failed to detect pixls as whitelisted because the Return-Path header entry is “pixls-verp-blah-blah@gmail.com” instead of “blah-blah-discuss.pixls.us”.
  2. Pixls’ server sends multiple messages in bursts of 5. This created a list of 5 “temp unavailable” entries in the spam log file.
  3. A second program, fail2ban, scans the spam log file looking for multiple entries of “temp unavailable” with the same IP address, and, finding more than one in a short period of time, blocks the IP at the firewall.

The IP 65.108.31.59 has been whitelisted in another way.

6

Yes we have an interesting mail setup so we don’t have to pay for it. It’d get pretty expensive if we used some service like mailgun or similar.

Thanks for reporting

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