On Mon, Feb 17, 2003 at 08:52:40PM +0100, Martin Stecher wrote:
No, I am not talking about an alias.
It is a very common SMTP behavior that one message is sent to multiple
recipients, especially if they belong to the same domain.
This happens in the SMTP dialog.
After the first HELO and MAIL FROM messages the sending MTA sends multiple
RCPT TO messages which get all acknowledged one by one.
The receiving SMTP MTA keeps the list of all recipients and delivers
to all of them (sometimes it needs then to create copies, sometimes not).
I would note that this is an optimization that not all SMTP
delivery agents (notably qmail) obey, since it complicates the client
implementation too much. RFC2821 (Sec 4.5.4.1) says its a 'SHOULD'.
It's also unclear on what to do if there are a huge number of
recipients at the same mail server (``a limit MAY be imposed'').
It works pretty well in real-life; all servers accept multiple
messages in a single transaction, most clients send them that way,
but you are still allowed to have lightweight clients which choose
to burn some bandwidth for the sake of robustness.
Especially for EMail no message must be lost. The OPES processor
is the thing that the user trusts, that has long experience what to
do with messages that cannot be delivered immediatly, how to manage
queues and so on.
If by 'lost' you mean 'silently dropped', then yes. I think it's
acceptable for the service to bounce messages back to the sender if
there's some kind of unrecoverable transport error, but silently
dropping them is very, very bad. And of course, the bounces should
be for rare situations!
-anil