Re: [exim] Is there and logical reason to reject mail from: …

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Συντάκτης: Tor Slettnes
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Προς: Exim User's Mailing List
Αντικείμενο: Re: [exim] Is there and logical reason to reject mail from: <> ?
On Wed, 2004-10-13 at 12:23, Greg A. Woods wrote:
> There is simply NO VALID EXCUSE for rejecting transactions with an empty
> return path when the sole recipient is the <postmaster> mailbox.


Oh, I can come up with an excuse, all right (basically, a fair amount of
phishing/spam is sent "From: <postmaster@...>" -- with alarming subjects
like "your account will be disabled" etc..; there is backscatter).

Whether or not it is a _valid reason_ is another matter, and IMO,
reading the relevant RFCs, it is a bit ambiguous.

Then again, even if an RFC says something, it is not neccessarily the
Universal Truth(tm). For instance, I note that you advocate rejecting
DSNs/bounces sent to more than one recipient. I am sure you know that
RFC2505, section 2.6.1, states:

| The most common case of such legitimate "MAIL From: <>" is to one
| recipient, i.e. an error message returned to one single individual.
| Since spammers have used "MAIL From: <>" to send to many recipients,
| it is tempting to either reject such mail completely or to reject all
| but the first recipient. However, there are legitimate causes for an
| error mail to go to multiple recipients, e.g. a list with several
| list owners, all located at the same remote site, and thus the MTA
| MUST NOT refuse "MAIL From: <>" even in this case.


Like you, I think that this RFC is wrong on this point (noting that this
particular RFC does not specify a standard, merely "best practices"),
and indeed I do reject DSNs to more than one recipient.

Similarly, because no outgoing mail is sent from <postmaster>, it is my
opinion that bounces to postmaster is perfectly rejectable, for the same
reason.

-tor