In mac OS Server, why don't virus & filtering settings seem to have any effect?

Question

In mac OS Server, when configuring the Mail service, it is possible to configure the virus & junk mail filtering settings. It's just a GUI front-end for clamav, amavis, spamassassin, greylisting, and RBL checking. But even with junk mail filtering enabled, spam is not affected--it still shows up in everyone's inbox, even though the spam score exceeds the "minimum score" set in the GUI.

Answer 1

Apparently the server team at Apple hasn't actually tested their filtering configuration in the real world, because the amavis settings do not actually stop any spam...they just tag it. Sometimes.

To get actual spam filtering to occur:

1. Open Terminal.app
2. sudo vi /Library/Server/Mail/Config/amavisd/amavisd.conf
3. Look near line 95 or so, and make the values look like this:

    $sa_tag_level_deflt  = -999;
    $sa_tag2_level_deflt = 4.0; 
    $sa_kill_level_deflt = 6.5; 
    $sa_dsn_cutoff_level = 10;

The "-999" forces amavis/spamassassin to add the spam level headers to every email, making it much easier for client-side junkmail filtering to do its job. The other levels are reasonable values for good filtering with few to no false positives.

4. Look near line 183 or so, and make the values look like this:

    $final_virus_destiny      = D_DISCARD;
    $final_banned_destiny     = D_DISCARD;
    $final_spam_destiny       = D_DISCARD;
    $final_bad_header_destiny = D_PASS;

This is really where the Apple guys failed to do the right thing. Mail that is clearly spam should be discarded, but the default is to pass everything...rendering the filtering basically pointless.