On Tue, Sep 02, 2014 at 02:51:08PM -0400, John C Klensin wrote:
Only when it's the SMTP greeting. In this case it's not.
That suggests that JCK's suggestion to have a new RFC to
replace 1846 is a good one, since it could mention this other
fairly obvious use case.
See draft-klensin-smtp-521code. If additional text is needed
there, please suggest some.
At this point there are already fielded MTAs that reject some
clients with 521 followed by a connection drop at times other than
the greeting banner. While such behaviour need not be officially
blessed, it needs to be tolerated by clients.
The most typical 521 response code scenario is when the connecting
client is listed by an RBL, but the server administrator prefers
to reject at "RCPT TO" so that the audit trail includes sufficient
envelope information.
We probably don't need to continue this thread on ietf(_at_)ietf(_dot_)org,
perhaps we're done, but if not, please redirect replies to a better
list.
--
Viktor.