SMTP and STARTTLS support (no replies)

hi,

i'm using HAProxy mainly to redistribute HTTP(S) requests to different
backends depending on their domain (via host header) to implement vhosts
on a single IP.

i'd like to have the same for SMTP, but unfortunately it's much harder,
since we get to know the target domain late in the SMTP-conversation
(RCPT TO:), but need to first present a proper greeting.
i guess this can be done as a lua script, but then we'd have to
implement STARTTLS, too.

are there any plans on implementing SMTP and STARTTLS directly in HAProxy?

it would need to handle the (E)HELO greeting, STARTTLS and fetch the
domain from the "RCPT TO:", so that this could be matched in an ACL.
the capabilities presented may be the intersection of all backends or
something we configure.
the rest of the conversation should be proxied to the corresponding backend.

cheers
pille