Seeking recommendation for anti-spam software

[Gabor Kovesdan]

Richard Coleman escribió:
> I am running a mail server using Postfix and Dovecot.  I would like to 
> hear people's recommendation for which port to use to add server side 
> anti-spam.  The problem these days is a richness of choices, so it's 
> hard to know port which to try.
>
> And call it a quirk of mine, but I really dislike (server) software 
> with a large number of dependencies.  That rules out Spam Assassin.  
> But I am fairly conversant with mail and Postfix/Dovecot in general, 
> so I don't mind any integration work.
>
> I apologize if this has been discussed before, but I just joined the 
> list (I am already on so many FreeBSD lists already).  I appreciate 
> any insight that people can offer.
>
Hello Richard,

I think the most common (and thus more mature) solution for this are 
amavisd-new + SpamAssassin + clamav, they have a lot of dependencies, 
though. Clamav catches all the viruses, just the spams had caused 
problems with this configuration, before I started to use postgrey.

I see your concerns about dependencies, but I think sometimes we have to 
make sacrifices for the most appropriate choice. This also applies to 
the next solution I recommend you and this is greylisting with postgrey. 
It does not have too much dependency, but it works in a way, that you 
can loose important mails as well.

The concept of greylisting is that the server responds to the sender 
with an error code meaning a temporary failure and places the sender to 
a list called greylist when a mail is being sent. After some minutes (5 
or so), well-configured STMP servers resend the mail, when your server 
notices, that the given server was greylisted, and now it can be 
trusted. Spam bots don't usually resend mails, they are too primitive 
for this atm. It can change in the future, but for now, the method 
works, it's been very well for me. The only problem is that there are 
STMP server that are configured in a weird way and they don't send out 
mails later again. Postgrey offers a solution, though. You can place 
such servers to a whitelist and they will be excluded from the greylisting.

I have heard good experiences about dspam as well, but haven't used it, 
thus I can't form any opinion.

Regards,

-- 
Gabor Kovesdan
FreeBSD Volunteer

EMAIL: gabor at FreeBSD.org .:|:. gabor at kovesdan.org
WEB:   http://people.FreeBSD.org/~gabor .:|:. http://kovesdan.org