... because they are bouncing.
In my ongoing attempt to investigate and fix problems of our mailinglist-server, i found that we only had a working bounce-detection for lists starting debian-* minus debian-private and the three digest-lists.
So i rewrote some parts of the bounce detection:
We now have four categories of lists:
- high (30 or more mails a day)
- medium (20 or more mails a week)
- low (10 or more mails a month)
- very-low (the rest)
for these four categories we calculate a spam-rate depending on the number of distributed messages and the number of bounces in the timerange of 24 hours for 'high' lists, 7 days for 'medium' lists, 30 days for 'low' lists and 90 days for 'very-low' lists.
If the Bouncerate exceeds 80% for unmoderated, and 60% for moderated lists, and bounces have been seen for more than 24 hours we kick. (these rates are subject to change, when we have implemented the warning mechanism)
So these changes implemented a bounce-detection for debian-changes-digest and today we reached the level of 60% bounces for more than 500 subscribers.
So what next?
To finish the bounce-detection, i want to implement something which tries to notify subscribers about bouncing mails. This is useless for 'hard'-bouncers, but people with some smaller problems like mail2news-gatewayers this could be helpful. I also want to implement something which sends out unsubscription notices for three weeks after the kick, so kicked out people can resubscribe after they have sorted out the problems.
Both should fire once a week per address.
What do you think?