Does sieve have control on relaying of mails at SMTP?
No. Sieve is designed to operate at or around the time of final delivery. The
language simply isn't oriented for use on MTAs. In particular, sieve provides
access to a limited amount of the envelope, the message header, and maybe at
some point the message content. Conspicuously absent from this list is access
to the sorts of information an MTA has and that are typically used to make
relay decisions, such as whether or not the client is considered to be
"internal" or "external", whether or not the session is authenticated, and so
on.
When I went through elvey's proposal on "refuse". Good one!
dontrelay :
Administrator of the domain can decide to accept the mails
but they donot want to relay mails to other. This requires
an extension "dontrelay" in sieve .
Even if you grant that use of sieve is appropriate in this context -- and I
don't think it is -- I have no idea what the semantics of a "dontrelay" action
would be. Sieve can cause messages to be redirected or rejected, but marking
them as being ineligable for subsequent relay seems pretty problematic to me.
Please share your comments on this.
I don't think it is an appropriate sieve extension.