Path: utzoo!attcan!uunet!dino!ux1.cso.uiuc.edu!ux1.cso.uiuc.edu!phil
From: phil@ux1.cso.uiuc.edu
Newsgroups: comp.mail.sendmail
Subject: A general question of mailers
Message-ID: <9300002@ux1.cso.uiuc.edu>
Date: 26 May 90 04:28:00 GMT
Lines: 32
Nf-ID: #N:ux1.cso.uiuc.edu:9300002:000:1783
Nf-From: ux1.cso.uiuc.edu!phil    May 25 23:28:00 1990


I know this is not the correct newsgroup for this question since it is of
a generic nature rather than specific to sendmail, but I cannot seem to
find a newsgroup dealing with issues of mailers delivering mail, the misc
group seems too light, and I suspect many of those in the know are reading
here anyway.

My question relates to the apparently conventional (standard?) practice
of validating a MAIL FROM: address before proceeding to accept the RCPT TO:
address.  I don't understand why this is done this way.  It seems to me that
things will work fine using other methods of mail delivery.

One of the problems with this practice by mailer programs is that long
delays often occur while the receiving mailer tries to validate the
MAIL FROM: address when domain servers are unreachable or unresponsive.
Many mailers assure single threaded mailing to any one host, which ends
up causing delays for all the mail waiting behind (I'd usually rather
not open 30 connections all to the same host anyway when my mailer suddenly
gets a batch of 30 messages from the mailing list server).

As to reliable return of mail, this is easily accomplished by recording the
HELO hostname with the mail control information until the MAIL FROM: address
can be verified.  If it cannot be verified, then rewrite the MAIL FROM:
address at that time naming the host it was received from, since I would
assume that host established reliable return by either verifying the
MAIL FROM: or rewriting to deliver back where it got it.

Can someone give me some explanations about this?  Is there a better place
that this kind of question should be posted?

--Phil Howard, KA9WGN-- | Individual CHOICE is fundamental to a free society
<phil@ux1.cso.uiuc.edu> | no matter what the particular issue is all about.