[Mimedefang] Question about filtering relays and recipients

[Dirk the Daring]

   I've been reading more in the mimedefang-filter man page, and I'm
unclear regarding some aspects of the section titled RBL LOOKUP
FUNCTIONS. I'm just not very good at Perl, I'm afraid - I'm an old C
hack, so program flow is not an issue, but the syntactical differences
keep tripping me up.

   Anyway, the man page is unclear on WHERE (in mimedefang-filter) the
relay_is_blacklisted_* functions should be placed. I would think that
filter_relay would be the place, but I'm not sure. Could someone clarify
that?

   I'm also looking for some example code using
relay_is_blacklisted_multi_count, including how to construct the array
of RBLs to pass to that function and how to properly evaluate the return
value (for example, to REJECT with X or more "hits" but not trip over
SERVFAIL or NXDOMAIN).

   Additionally, I'd love to use the md_check_against_smtp_server
function, but I'm not sure I can. In my environment, where I host a
number of Domains, the MIMEDefang server could relay to any one of 4
other servers. That is, "bob at domain1.tld" might have his mailbox of
"server1.domain1.tld" while "jane at domain1.tld" has her mailbox of
"server2.domain1.tld" and "john at domain2.tld" has a mailbox on
"server1.domain1.tld". Sendmail deals with this thru the use of
mailertable and virtusertable.

   Do I need to employ stream_by_recipient ? Or should I use the
SOCKETMAP functionality (I do have sendmail v8.13.4) to have MIMEDefang
query virtusertable and mailertable? For that matter, as MIMEDefang
looks at these E-Mail addresses, is it seeing them *before* or *after*
sendmail has run thru aliases, virtusertable, and mailertable? Does
anyone ever have an environment where they host multiple Domains
across multiple interior servers?

   Also, does the SMTP server against which the "check" will be done
need to support VRFY? If not, are there any of the usual anti-SPAM
settings in sendmail (e.g. needhelo) that should be avoided so that
MIMEDefang can place its query?

   Thanks again to the MD community for the assistance.

Dirk