Sendmail Sender Verification

[Rose, Bobby]

I've been using milter-sender with sendmail for quite awhile to do this
with good success.

http://www.snert.com/Software/milter-sender/

But it still won't stop a spammer or virus from using a valid email
address but will stop bogus ones.  It also can do some other checks on
the sending system.

-----Original Message-----
From: MailScanner mailing list [mailto:MAILSCANNER at JISCMAIL.AC.UK] On
Behalf Of Mike Kercher
Sent: Tuesday, March 30, 2004 1:28 AM
To: MAILSCANNER at JISCMAIL.AC.UK
Subject: OT: Sendmail Sender Verification

I've been noticing more and more log entries from aol.com lately similar
to the following:

Mar 29 22:18:24 avwall sendmail[29603]: i2U4INJU029603: from=<>,
size=3001, class=0, nrcpts=1,
msgid=<200403300421.XAG19946 at rly-xk01.mx.aol.com>,
proto=ESMTP, daemon=MTA, relay=omr-m11.mx.aol.com [64.12.138.23] Mar 29
22:18:30 avwall sendmail[29620]: i2U4INJU029603:
to=<username at somedomain.com>, delay=00:00:07, xdelay=00:00:00,
mailer=local, pri=123001, dsn=2.0.0, stat=Sent

I assume that the omr- stands for Open Mail Relay or something of the
sort and I also assume that it is verifying that the email address is
deliverable prior to delivering an email from an address to the final
AOL recipient.  I suspect they are doing something like this to combat
their massive spam flow.

Has anyone implemented anything like this with sendmail.  I know it
would introduce additional network traffic, but might it be worth the
trade-off?
Thoughts?

Mike