understanding e-mail server amavis
 

Hi,

I'm trying to understand how to set up an e-mail server. I did it, to some extent. Someone told me to install postfix, dovecot, amavis, spamassassin and clamav.

But I still don't understand what amavis does exactly, or to be more specific, what it does and spamassassin + clamav doesn't.

Could you explain and/or point me to some references? It seems awfully complicated, given how many daemons are involved in setting up an e-mail server.

Following a tutorial, I also installed procmail, which I'm not even sure it does its job of moving mail automatically to the Spam folder. I created the recipe and when sending a spam test, it didn't seem to work (checked in the linux cli, without dovecot basically), but when I connected through an e-mail client (having configured dovecot), the mail was automatically moved to a spam folder. I'm not even sure if the e-mail client or procmail did that :)

Amavis is not a mail server. It's a content filtering S/W that uses clamav and spamassassin to check an email for viruses and identify if it's spam or not. Read more here


I suggest you to try zimbra, either the free (open source) edition or the paid (network) edition.
It uses postfix and amavisd, along with other tools that makes administration easy through a web interface

Regards

Well, I wanted first to understand how things work at a 'basic' level, as it were. The classical way, as it were. Even if it's harder, I want to see how it behaves exactly, the logs and so on.

I know amavis is not an e-mail server, never thought it was. But I don't understand exactly the relationship between amavis and spamassassin + clamav. When I read about amavis, it says that it filters spams, viruses and so on. Then my obvious question is, what do the other daemons to, then?

amavisd is a daemon running usually on a mail server in order to check emails.
In a default setup it accepts mail and after doing its tests it passes it to the real MTA
To check email for viruses it connects to the socket of a running clamd instance (this is done for speed). If mail is infected it goes to quarantine, else it goes to the next step (spam check or delivery)
Spam filtering is not mandatory, but if you enable it, amavisd will use spamassassin for this
You may see the diagram here to better understand the email flow in a mailserver using amavisd

Regards

All right, things are becoming slightly clearer, and yet again, why can't you simply use spamassassin + clamav? This is what I've installed now and my e-mail server seems to be working, more or less. Why would I also need amavis, if spamassassin is already testing e-mail for spam and clamav is searching for viruses?

You can use separately spamassassin and/or clamav, but IMHO it's better to use a daemon that integrates them both.
Besides while spamassassin is designed to be used by an email system, clamav is an antivirus, so it needs some more things to work with emails (like a milter or something).
Amavisd is doing this transparently, so you don't need to bother.

Regards