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Re: Bounce/System Notification Address Verification

2005-06-30 05:02:45

On Thu, 30 Jun 2005, Matti Aarnio wrote:

On Thu, Jun 30, 2005 at 11:03:50AM +0200, Arnt Gulbrandsen wrote:
Hector Santos writes:
But the reason according to your server is the space in the MAIL FROM:
<> command as a syntax error.

Ok, wow!!!

You better reconsider being more relaxed with that MAIL FROM: strict
syntax I'm sure you will get hit by other servers

In the past week, 100% of the mail arriving at work with
     MAIL FROM: <...
     RCPT TO: <...
was spam. Good fodder for bayesian analysis.

(Btw, I didn't discover this; der Mouse told me.)

As far as I know all commonly used MTAs use correct syntax when sending mail out and so when email is transmitted from remote network it would
be fine. But it is also true that some SMTP-specs incompatible MUAs exist
that use "MAIL FROM: " so it might not be good idea to drop email from
local users who are trying to submit email if you know that those users
can't use any other MUAs.

As far as anti-spam techniques what happens is that some percent of
messages come directly from spammer controlled PCs and it appears some spam software indeed was designed to mimic those badly written MUAs and also do not work properly (or its possible that some spam software
in fact directly tries to interface with those bad MUAs to send email
out). So its exactly those MUA->MDA spam attempts that would be caught
by such anti-spam technique.

I would have used strict-rfc822 mode in my work production systems,
if it would not reject something like 95% of users who send thru their
ISP master relays...

Its not RFC2822 at all. And its always been this way in email:

RFC772 (I think its first genuine RFC with MAIL FROM  - published in 1980)
on page 8 gives the following syntax:
 MAIL <SP> FROM:<sender> [<SP> TO:<path>] <CRLF>

RFC821 (published in 1982) in section 3.1 gives the following syntax:
 "MAIL <SP> FROM:<reverse-path> <CRLF>"

RFC2821 (published in 2001) gives the following syntax:
 "MAIL FROM:" ("<>" / Reverse-Path)
                       [SP Mail-parameters] CRLF
Reverse-path = Path
Path = "<" [ A-d-l ":" ] Mailbox ">"

MS Outlooks do put those extra white-spaces in there blatantly..

Ok, so we find that Microsoft email software is not SMTP compliant in yet another way. Something new and unexpected? Don't think so!

The point is to remember what standard specs say and not give in and allow
for incorrect behavior just because one large vendor says so.

William Leibzon
Elan Networks

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