[unisog] Email for life

Daniel Feenberg feenberg at nber.org
Mon Mar 22 13:12:30 GMT 2004

I wouldn't start up such a system with an MTA that could keep the system
from being overwhelmed by spam, virus traffic and support calls. At a
minimum, it would need to be able to:

1) Reject spam and virus traffic during the SMTP transaction, rather than
discarding mail later, or (worse) generating DSN mail. This isn't an easy
ability to find - Can-it is the only such package I am aware of for
Sendmail. Spamassassin could be run within a milter to do this, if you
have the skills.

2) Reject mail to overquota mailboxes. Note that if you offer pop service,
sendmail (strictly speaking, the sendmail local delivery agent mail.local)
can't do this right, since once the mailbox is more than half full, pop
can't make a working copy of mailbox without busting the quota, and
therefore won't allow the user to process his mail (including deleting
messages). There is an "FSTAT" patch for sendmail that could probably be
modified to make sendmail respect quotas in a practical way or procmail
could be so programmed (but that wouldn't happen during the SMTP
transaction, so you would be sending DSNs for overquota messages, many
of which would be going to forged return addresses). Perhaps other MTAs
are better at this.

3) Delete old uncollected messages (easy - archmbox does this)

4) Reject mail for unused mailboxes. That is, if mail has not been
collected from a mailbox for N days (perhaps 30), incoming mail for that
mailbox should be refused during SMTP transaction phase with a message
such as "Mailbox inactive". Such mailboxes tend to receive only spam and
virus traffic, and often receive a lot of it! Perhaps FSTAT could be
modified to handle this. Once the user took an interest in the account (by
checking for mail) the last used date would be current, and mail would be
accepted again.

There is a problem now running a forwarding service, in that if you
forward spam and the user complains to his/her ISP, a clueless or careless
ISP may put your MTA on a blacklist rather than the source of the spam.
Other than being very carefull about what you forward, I don't know a
solution to this problem.

I understand these comments are sendmail oriented - I'd be glad to hear
from anyone with another MTA that does better.

On Sun, 21 Mar 2004, Greg Francis wrote:

> Gonzaga provides e-mail for life. They can either forward or retain their 
> mailbox. The alumni mailboxes do have a lower limit than the student ones 
> though. The biggest problem we have is spam accumulating in unused alumni 
> mailboxes; we periodically purge those mailboxes that haven't been used in 
> a long time that have excessive spam in them.
> Greg
> > >From "Hall, Rand" <rand at merrimack.edu> =====
> > >What are you all doing for "email for life" systems?
> > >
> > >Forwarding only? Full mailbox? Outsourcing?
> > >
> > >Some people here are starting to ask questions :-)
> > >
> > >
> > >Cheers,
> > >Rand
> > >--
> > >Rand P. Hall, Director, Network Services
> > >SunGard Collegis, Inc.
> > >Merrimack College, North Andover, MA, USA
> > >P:978-837-5000
> > >F:978-837-5383
> > >Rand.Hall at merrimack.edu
> -- 
> Greg Francis                                Gonzaga University
> Sr. System Administrator                    Spokane Washington
> francis at gonzaga.edu                         509-323-6896

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