[sllug-members]: Greylisting?

[Doran L. Barton]

Not long ago, Mark K. Spute proclaimed...
> Thanks to everyone who helped out with my SSH problem.  The server works 
> great now and logging is is fine too.
>
> Now I have to figure out a way to reduce the amount of spam that I am 
> getting.  I have installed spamassassin, but am still training it. However 
> I happened across an article on greylisting which saves CPU cycles by 
> rejecting some spam before it even gets to spamassassin.
>
> Has anyone else on this list tried greylisting?  What were your 
> experiences?  Would you recommend it?  What software did you use?  Do you 
> have any recomendations to a total noob who is trying to make his mail 
> server more user friendly?

Yeah, I've used milter-greylist on dozens of servers and it reduces a lot
of spam, but I really think it's only temporary. I think spammers will
devise methods to circumvent greylisting. For the time being, though, it
works great.

There are a few different greylisting implementations available. The
postgrey program seems to be a favorite for Postfix users. I mentioned
milter-greylist above and while it's not completely straightforward to get
up and running, once it is running, it runs very reliably. 

I recommend gettign the 4.x version tarball from the website and building
an RPM from it:

    $ wget ftp://ftp.espci.fr/pub/milter-greylist/milter-greylist-4.0.tgz
    $ rpmbuild -ta milter-greylist-4.0.tgz
    $ sudo rpm -Uvh ~/rpm/RPMS/i386/milter-greylist-4.0-1.i386.rpm

One thing I've found is that the RPM doesn't set the ownership of the
/var/milter-greylist directory properly:

    $ sudo chown grmilter:grmilter /var/milter-greylist

Then, add this line to /etc/mail/sendmail.mc:

    FEATURE(`milter-greylist')dnl

Create sendmail.cf:

    $ sudo make -C /etc/mail

Enable the daemon to start at boot time and start it up:

    $ sudo /sbin/chkconfig milter-greylist on
    $ sudo /sbin/service milter-greylist start

Restart sendmail:

    $ sudo /sbin/service sendmail restart

Now, you'll want to edit /etc/mail/greylist.conf and tweak some settings to
your liking. The default behavior is to whitelist everything. To greylist
everything, you'll want to scroll to the bottom of the file and replace

    acl whitelist default
    
with something like this:

    acl greylist default delay 10m autowhite 45d

Then, restart the greylist milter:

    $ sudo /sbin/service milter-greylist restart

-- 
Doran L. Barton <fozz at xmission.com> - Linux, Perl, Web, good fun, and more!
 "Dinner Special -- Turkey $2.35; Chicken or Beef $2.25; Children $2.00"
    -- Seen in newspaper ad
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