I like the fact that qmail puts everything into the queue as
separate transactions, even for a single message with multiple recipients
(one sender, one recipient, one message, one connection). However, it is
not an SMTP requirement, and many MTAs will send the same message to
multiple recipients in a single connection, if the MXes are the same for
all.
If I'm going to reject an email, I generally do it during the
connection, so that I don't have to accept responsibility for it. It also
means I don't have to process it further internally, when only some of the
recipients want to accept it.
However, this leaves me with a quandry: If I reject the
connection, I reject it for everyone, including a recipient who may have
wanted it; if I accept the connection (full transaction), I accept it for
everyone, including a recipient who may not have wanted it - the internal
processing mentioned earlier.
If I only allowed a single sender/recipient/message per
connection, then it would be easy to apply the rules and either accept or
reject the connections individually.
<QUESTION> what would be the implication for multiple recipient
connections if each additional recipient generated a 4xx error?</QUESTION>
Would the sending server DATA for the first recipient and
reconnect for the next ones?
Would it depend on the actual error code?
Would it retry, later, and do the same thing again? (I'd hate to
see it keep doing this until a timeout, only to fail completely, when only
some of the recipients wanted to reject the connection.)
Enquiring minds (mine!) want to know. Thanks for your opinions,
theories, and most of all, facts.
