Dick St.Peters wrote:
Only if the remote MTA cannot be reached should the
message be accepted and stored for later delivery.
yes, a key reason why its hard to see why bounces should
go away entirely.
Yes, but very much a corner case at most. Border MTAs
should have all the information necessary to determine if
a message is acceptable to deliver (e.g. list of valid
users). The only time this might be appropriate is in
the case of multi-hop e-mail accross administrative
boundries.
Even a list of valid users won't eliminate bounces. That a
user is valid doesn't mean his/her mailbox isn't over quota
or isn't forwarded to a mailbox that's over quota or to one
that's temporarily disabled but returning 5xx error codes.
The on-the-fly delivery concept is also fatally flawed. The
very reason for having multiple MXs is to receive mail when
the primary MX is too busy to accept new connections.
ACK. There's no way to get completely rid of backscatter and
bogus bounces without "reject on SPF FAIL".
PRA, DKIM, a hypothetical 2821bis, and call-forward tricks,
nothing will change this: SMTP without "reject on SPF FAIL"
is doomed.
Bounces can be greatly reduced but not eliminated completely.
+1 Bye, Frank
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