Secondary MX user list filter for Sendmail
Todd Vierling
tv at duh.org
Wed May 19 01:24:29 UTC 2004
A colleague asked me offlist about how to make a Sendmail secondary MX
properly return 550 for invalid recipient addresses. For smaller sites --
or even larger sites if the list is autogenerated and the access_db uses
"btree" storage (it's rather fast) -- the below solution will do just that.
=====
In your secondary MX's sendmail.mc, add the following FEATUREs if you don't
already have them.
FEATURE(`access_db')dnl
FEATURE(`blacklist_recipients')dnl
Rebuild your sendmail.cf from this, and then put entries like the following
in your /etc/mail/access file (assuming "foo.com" is your domain). I'm also
assuming that "foo.com" is already in /etc/mail/relay-domains (or
/etc/mail/sendmail.cR depending on your sendmail install), so that relayed
mail can get through.
userone at foo.com RELAY
usertwo at foo.com RELAY
To:foo.com "550 User unknown"
The RELAY lines designate explicitly allowed recipient addresses for
relaying to the primary MX. The To:...550 line, which requires the
"blacklist_recipients" feature, is a fallback rule that matches after the
email addresses and returns the expected "User unknown" error.
Now rebuild your access.db file, restart sendmail, and voila, you have a
secondary MX explicit user list.
--
-- Todd Vierling <tv at duh.org> <tv at pobox.com>
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