ned+ietf-smtp(_at_)mrochek(_dot_)com wrote:
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.
The names we have for this three-state logic in our code are, with
apologies to Sergio Leone, "good" (2yx), "bad" (5yz), and "ugly" (4yz).
> There's a reason we call it the ugly case.
Speaking one implementation only:
For our list server MTA making the distribution, we have two transport
modes - Direct Smart Host SMTP server vs the old UUCP/UUCICO transport
mode.
The latter option it will make a copy for each member. So we have
customers who will use that old mode, but this time saving the
.XQT/CMD/DAT files in the queue that the SMTP router eyeballs for
outbound. This gives them the singular sends and retries.
But in direct SMTP connect mode, a 1 copy for all method, the 5xx
response will auto-unsubscribe the member, and 4xx just skips them for
the specific transaction - "'tough titty!' said the cow the cat to the
cow when the cow went dry." Doesn't unsubscribe them but they don't
make that one distribution.
But as you said, the ugly has been when the 4xy should really be
permanent. Our solution is a list moderator defined error limit
option (default 3) when it begins to auto-unsubscribe the 4xx member
distribution response.
Of course, when there is the real but rare rare false positives, users
will report and compliant.
So I don't think it has been a big issue that required attention.
--
Sincerely
Hector Santos, CTO
http://www.santronics.com
http://santronics.blogspot.com