You have discovered the difference between the envelope of a message,
and the headers of a message.
Ever notice how spam often gets delivered to your mailbox, yet doesnt
have your address on the To: header? The _envelope recipient_ is you,
even though the To: header is arbitrary. Some legitimate mail is like
this to, such as mailing lists you've subscribed to. The To: header has
the list address, but the list software sends out messages with the
envelope sender set to each subscriber.
As mentioned in a following message, and envelope sender of <> is a
special case, usually use by mailers sending nondelivery reports, to
indicate that if the nondelivery report cant be delivered, to not send
another nondelivery report (can you say "mail loop"?).. Sometimes
autoresponders use the null sender to prevent loops as well.. (dueling
autoresponders ;)) Any message sent automatically by program in reply
to another message should usually use the null sender. (Lets say you
send a message to your friend, and then immediately go on 'vacation'
(and your sysadmin sets up a 'vacation' responder on your system.).
Lets say your friend is also on 'vacation', and has a similar
auto-vacation message. If the autoresponder didnt use the null sender,
then when you both came back from your two week stay in bermuda, each
of you would have a few billion messages waiting for you, assuming you
didnt exceed any mail quotas, or the mail servers didnt crash, etc...
(The short answer to your question is becuase RFC dictates that it do
so)
On Sat, 30 Dec 2000, Peczoli Zoltan wrote:
> Hello all,
>
> My question is why does Exim accept a simple <> in the 'From' part of the
> SMTP conversation?
>
> It goes like this:
>
> 220 myserver.com ESMTP Exim 3.16 #1 Sat, 30 Dec 2000 17:48:53 +0100
> HELO myclient.com
> 250 myserver.com Hello myclient.com [1.2.3.4]
> MAIL FROM: <>
> 250 <> is syntactically correct
>
> Is this the desired behavior?
>
> When receiving such mail, the From line appears as "Remote Mail Delivery
> System <>"
>
> How can I reject messages with <> in MAIL FROM part?
>
> Thanx:
> Pocok
>
>
>
> --
> ## List details at http://www.exim.org/mailman/listinfo/exim-users Exim details at http://www.exim.org/ ##
>
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