> I have also been unscribed on 4 or 5 occasions over the last couple
> of years, usually when my company's net is down for several hours,
> but certainly less than 24 hours.  It seems that the mail system
> should try somewhat harder before it drops someone from the list. By
> the way the FreeBSD mail server usually drops me at the same time,
> so I assume it is a freature of the software being used, not a local
> policy.

The formula is that there has been more than 50 more failures than
successful deliveries to a given address.  Each time a bounce is
received, a counter for that address is incremented by two.  Each time
a message for a list is sent out, all counters are decremented by one.
If the counter is greater than 100, that address will be unsubscribed
the next time I process the bounces.

The algorithm is designed to be fair to transient outages and also be
fair to the mailing list maintainers.  

	--jtc