Re: Sender header?

[Stainless Steel Rat <ratinox@peorth.gweep.net>]

* prj@po.cwru.edu (Paul Jarc)  on Thu, 24 May 2001
| But your interpretation requires more than that.  It's not enough just
| to give random-sending-host.domain.com an MX record pointing to
| mail.domain.com - mail.domain.com must also accept mail explicitly
| addressed to random-sending-host.domain.com, even if it would
| otherwise only accept mail addressed to domain.com itself, because you
| would put random-sending-host.domain.com in Sender, and Sender must be
| a mailbox of the person who sends the message.

Yes, it should.  In fact, it must.  That is the nature of DNS.

| Where does 2822 say that Sender must identify the host used to send
| the mail?

The canonical mailbox is required by RFC 2822.  login @ FQDN is the most
canonical name for any given user.

| > Proper mail handling depends on that being the case.
| What breaks when Sender does not identify the host the mail was sent
| from?

The correct question is, what breaks the Sender field does not canonically
identify the sender?  The answer is, if the Sender field does not contain
the canonical mailbox of the sender and there is a problem, perhaps with
that machine, I may be unable to contact the sender.

You see, Sender is for human consumption only.  It exists at least
partially so that humans, like me, can track down problems at their
source.  If the Sender field does not include the FQDN of the sending host
it makes finding and solving problems that much more difficult.

| > If your host has neither A nor MX records then it is not configured
| > correctly.
| Right, but the A and MX records aren't the problem.

Correct, they are the solution.
-- 
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