Validating incoming email addresses

karlp at karlp at
Mon Jun 27 18:00:30 UTC 2005

> On Fri, Jun 24, 2005 at 10:50:43PM -0600, karlp at wrote:
>> How do I go about blocking incoming email based on validating the
>> sender's
>> email address? I am getting spam email which is from a non-existent
>> email
>> address on my own domain. A look at the header shows it's not from my
>> domain. I expected that. But, the From: field is from my domain
>> (, even down to my server name
>> (
>> which NEVER sends email, per se, other than internally as in mail
>> generated by cron jobs.
>> Too much information, but I hope you get the gist of what I need.
>> TIA,
>> Karl
> Depends on your email setup and where you want to stop the mail.  If
> you want to stop it at the door, then it depends on what MTA
> (sendmail, postfix, et al.) you are using.
> If you want to punt it after your MTA accepts it but before delivery,
> I strongly recommend SpamAssassin.  With or without SA, you can drop
> it in the bit bucket with a well-crafted recipe in your ~/.procmailrc
> (assuming procmail is your MDA (delivery agent)).  But with SA, and
> assuming SA scores it as spam, then procmail can (1) divert the spam
> to a bucket for inspection, (2) punt spam scoring over XX points, or
> (3) summarily punt all identified spam (not recommended), or some
> combination.
> Let us know your constraints.  I'm well versed in Postfix and
> SpamAssassin.

I'm using sendmail and Spamassassin (v3.0.2) and these emails aren't
getting caught. I have some other issues as well, such as email that is
clearly, to me, spam which is not being caught. The score is only .1 (my
threshold is set at 1.0) I guess in theory, my threshold should be 0.0
rather than 1, but there are a bunch of emailers who have no clue and
insist on 'pretty-ing' up their email by sending HTML email (curse the
fool who came up with that functionality; and curse AOL for not allowing
anyting BUT HTML email!).

I have a pretty complex set of procmail filters at both the enterprize
level and the personal level in my own account. I'm no great procmail
programmer as many of my rules are copied/tested and retested until they
work 'right'. I may be wrong, but optimally, I think I'd like to have
sendmail refuse delivery of email which isn't a user on my domain. However
if it's better to have procmail do it, I'm all over that, too.

Thanks Bob. (and any others who have experience and can help)


> Cheers,
> --
> Bob McClure, Jr.             Bobcat Open Systems, Inc.
> robertmcclure at
> God doesn't have (or need) a Plan B.
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