OT: Mail list cleaning

Michael H. Warfield mhw at WittsEnd.com
Fri Mar 13 21:09:24 GMT 2009

On Fri, 2009-03-13 at 20:21 +0000, Paul Welsh wrote:
> Hi

> Apologies this is off-topic, but can anyone recommend an application for
> cleaning email lists, ie, checking whether the address is still valid but
> not sending a message?

	It's the "but not sending a message" that's going to get you.

	Most listserver packages I've used have some method of catching most
bounces and automatically unsubscribing most of them.  Unfortunately,
there's always some dain bramaged MTA which just absolutely refused to
give you enough information back (Exchange use to be the WORST), and it
gets even worse when someone has subscribed another mail exploder
compounding the problem.

	I use to run some majordomo lists years ago and that one didn't do a
very good job of autocleaning.  One of our larger lists (several
thousand subscribers) was slowing down so bad the latency was getting
out of hand.

	I came up with a janitor program that would run monthly and took
advantage of the "+" extensions and then sent everyone an individualized
message from the list name "+" an md5 hash extension I could intercept
for any bounces.  The hash was in the subject, in the body, in the
message id, in the from, in the reply-to, in the errors-to, and in the
envelope From_.  If I got anything back (and that included people who
wanted to unsubscribe and were too clueless to read the instructions)
they were dump from the list.  After that, I was seeing some of my high
subscriber / high turnover lists clean out as much as 10% a month in
churn and the performance shot right back up.  Never got a single
complaint.  Even got a few compliments.  I explained in great detail why
they were getting the reminder and even that they could unsubscribe, if
they wished, by replying.  Caught a few people with misconfigured
autoresponders (I had Precedent: bulk) so I was even performing a public
service and the frequency of autoresponder complaints on my lists also
dropped off as the subscribers wised up.

	But you have to send a message.  Many many sites disable EXPN and VRFY
on the MTA so you can't tell that way (spammers and hackers were abusing
them to identify targets).  Even then, it wouldn't help with aliases,
relays, other mail exploders, and subsidiary lists.  You have to send a

Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0xDF1DD471        | possible worlds.  A pessimist is sure of it!

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