I administrate two Mailman mailing lists at ScienceByEmailHTML and ScienceByEmailPlain. We have approximately 39 000 addresses in the former list, and about 1000 in the latter. I have a question about the bounces we receive.
We have the lists set so after five bounces, the address is automatically disabled. An notification is sent alerting us to the disabled account, where we then delete the address from our own records as well as Mailman.
Mailman will automatically delete members with delivery disabled by
bounce according to the settings bounce_you_are_disabled_warnings and
bounce_you_are_disabled_warnings is set to 0, the member will be
removed immediately after the disabling bounce is received.
Depending on the week, we can get over a hundred of these notifications which come in batches, arriving typically on Friday (although we also get waves coming in on Monday as well).
This is strange. Unless you only post on Friday's and Mondays, or
unless there is some unusual reason for the bouncing addresses to "go
bad", I would expect bounces to be uniformly distributed over the days
there are posts.
Also, I find it possibly unusual that even out of 40,000 addresses that
100+ per week "go bad", but maybe not.
However, we can also go a week without receiving a single one. Given the spread of excessive bounces is often in excess of a hundred, and rarely fewer than 60 or 70, I'm wondering if you know why this might be the case. Also, why do they arrive in waves? Is it collated and sent periodically through Mailman, or is it a result of batches of bounces being sent back from servers?
Mailman collects bounces and processes them in batches, but this
depends on the Defaults.py/mm_cfg.py setting REGISTER_BOUNCES_EVERY
which defaults to 15 minutes, and even if it were for some strange
(and probably misguided) reason set to something like 5 to 7 days, I
would still expect "bounce day" to be more variable.
You need to check Mailman's 'bounce' log to see when bounces are being
received/registered, and Mailman's 'smtp-failure' log for potential
delivery issues. You also need to look at the actual bounce
notifications attached to the disabled notices to see that these seem
to be legitimate bounces.
Mark Sapiro <mark at msapiro.net> The highway is for gamblers,
San Francisco Bay Area, California better use your sense - B. Dylan