Path: utzoo!attcan!uunet!samsung!usc!ucsd!brian From: brian@ucsd.Edu (Brian Kantor) Newsgroups: comp.mail.sendmail Subject: Re: A general question of mailers Message-ID: <13972@ucsd.Edu> Date: 27 May 90 15:02:03 GMT References: <9300002@ux1.cso.uiuc.edu> Organization: The Avant-Garde of the Now, Ltd. Lines: 30 I disagree that the SMTP 'Mail From' shouldn't be parsed - but I think most sites are doing it the wrong way. What I think is proper is to check it for syntax, and if the syntax of the MAIL command is incorrect, abort the transfer with an appropriate protocol error message. Otherwise accept it, and go on. Where most mailer's errors come in doing the above is that they run the hostname in the FROM command through a canonical hostname lookup, and that causes big delays on some SMTP transactions. It's silly to do the canonical hostname lookup at that point. If the mail is deliverable, you don't need to do it at all, and if the mail isn't deliverable, you can do it when you return the mail. The only reason for checking the address supplied in the FROM command at all is to warn the sender of problems with his mailer - since that moment is presumably the only time you have any way of getting in touch with him - after all, the address is invalid, so you can't mail him a failure notice. I suspect a lot of sendmail.cf files have hostname canonicalization (is that a word?) in places (such as ruleset 3) where the FROM command gets run through the hostname processing. Seems to me that canonical hostname substitution need only be done later on, when preparing the message for delivery. I'm pretty sure we do the same stupid thing in our sendmail.cf file. I'll have to look into fixing that. - Brian