Re: VGER's filters..

Matti Aarnio
2003-04-04T20:54:02Z

On Fri, Apr 04, 2003 at 12:36:20PM -0800, H. Peter Anvin wrote:
> By author: Matti Aarnio <matti.aarnio@zmailer.org>
> > <<- MAIL FROM: <yahoo-dev-null@yahoo-inc.com>
> > ->> 501 5.1.7 strangeness between ':' and '<': <yahoo-dev-null@yahoo-inc.com>
...
> Sendmail, and a whole bunch of other mailers, have taken the more
> liberal approach of allowing any RFC 822-compliant address in this
> place (which is a *lot* more liberal than an RFC 821-compliant
> reverse-path.) This is consistent with the "be liberal in what you
> accept, conservative in what you send" philosophy of network
> interoperability.

Definitely. VGER is running fairly liberal mode, while some
other systems I run in extremely strict mode. As a result,
vger lets in spams, which could be blocked by running strict.

> I suspect in Sendmail it naturally falls out of using a single set
> of canonicalization rules for all syntax.

Nope, the protocol line parser in original version was simple,
it reused same code for "MAIL FROM:" and "RCPT TO:" as for
"From:" and "To:", therefore with old sendmails you could
do in SMTP:
MAIL FROM: < foo@bar >
MAIL FROM: foo@bar
and I think even:
MAIL FROM: Example User foo@bar

There really was no SMTP protocol parser, there was just something
resembling it on surface. (And tons of security problems...)

> -hpa

/Matti Aarnio