Subversion Repositories greylisting

SENDMAIL ISSUES:
 
While many people still use relay-domains to specify the domains you wish
to allow sendmail to relay for, I consider it to be deprecated, and
discourage the use of relay-domains.  A better, more flexible, and safer
alternative is to use the access db functionality of sendmail, which
relaydelay will observe (if enabled).

If you have any entries in your relay-domains file, it is strongly
suggested that you remove them and place them in the access file
instead.  You can even specify which type of relaying you wish to allow
by using the appropriate tag To: or Connect: tags on the LHS.

For more information, please see:

http://www.sendmail.org/~ca/email/doc8.12/cf/m4/anti_spam.html

Enable the access db functionality in sendmail by adding the following
to your sendmail.mc and recompiling:

FEATURE(`access_db')



SENDMAIL ACCESS DB HANDLING BY RELAYDELAY:

For those interested in the precedence ordering of the milter's access db 
checks, here are the order that checks are done:

First, the greylist database is checked if there is a matching record (full
or partial) for the relay or recipient.  If there is a record, no further 
whitelist/blacklist checks are done, and the mail is handled according to 
the settings in the record.  If there is no record found, then the milter 
continues on to check the access db.  

For the access db checks, first we check to see if there is a Connect: 
tagged or generic (untagged) entry for the relay ip and dns name of the 
client.  If an entry is found, and the value is set to "RELAY", then 
checks are bypassed.

If either an entry is not found, or the found entry is not set to RELAY, we 
then check for Spam: tagged entries with the recipient's address and domain 
information, and if an entry is found and the RHS is set to FRIEND, then we 
bypass the checks.

In this manner, we can change the default behavior of the milter to be 
either opt-in or opt-out for a particular domain.  For example, a set of
entries like this:

Spam:somedomain.xx         FRIEND
Spam:user@somedomain.xx    HATER

will cause the milter to greylist mail for user@somedomain.xx, but mail 
for all other users at somedomain.xx will not be checked.

Of course, it is more desirable to put exception rules in the greylisting
database for both performance and reporting reasons.  But the milter now 
supports checking the access database so as not to require system 
administrators to keep both updated (since sendmail defaults to not allow
relaying unless there is a matching entry in the access db).

NOTE: The greylisting db does not yet support white/blacklist entries 
  based on the dns name of the relay.  If you need dns based entries,
  you have to use the access db.