Tony Finch wrote:
On Tue, 5 Aug 2008, SM wrote:
If you are going to temporary fail the transaction because the first
recipient got a 4yz reply, you may end up never being able to attempt a
delivery for the other recipients.
I know that, but there's evidence that some implementers don't understand
it.
Interesting, I have not seen it myself, but wouldn't be surprise.
I guess, if given the chance, it should be made clearer.
IMV, it depends on the client, is it a MUA client? an backend server
list distribution?
Overall, the implementation where it attempts to satisfy all and keeps
trying in new sessions until the very last one is resolved, would be
more difficult, wasteful and prune to error - especially in a list
distribution. But of course, its not impossible to do.
In fact, I believe some MUAs will not even continue with the DATA
until all same session RCPT are positively resolved. I have to double
check if this was because of 5yx responses only, but under ThunderBird
if I tried to send to my server which checks for local valid
recipients, an address among a few that is invalid, it will not
continue sending it until it is fixed or removed from the TO:, CC:,
BC: address list. I'll be interested to try this later by forcing a
4yx response instead to see how the MUA will behave.
In either case, this MUA behavior would not be very acceptable for a
automated backend MTA.
--
Sincerely
Hector Santos, CTO
http://www.santronics.com
http://santronics.blogspot.com