This patch implements two extensions to the ConfSourceSQL.pm module of 
SpamAssassin:

1) An alias table feature, where you can define as many aliases of an address as
   you want. SpamAssassin looks if $username is an alias for another username, 
   and sets $username accordingly.

   You first have to create an aliases table in MySQL like this:

   CREATE TABLE `aliases` (
     `id` int(11) NOT NULL auto_increment,
     `username` varchar(100) NOT NULL default '',
     `alias` varchar(100) NOT NULL default '',
     PRIMARY KEY  (`id`),
     KEY `username` (`username`)
   ) TYPE=MyISAM;

   The "username" columns takes the real user names; the "alias" colums takes 
   its aliases, one alias per row.

2) If the username contains an "@" sign and only characters that are valid for 
   domain names after it, additional WHERE-clauses get appended to the SQL 
   querystring. Example:

             $username is: "jonas"              (already existing functionality)
   SpamAssassin looks for: "jonas"
                           "GLOBAL"
                           "@GLOBAL"

             $username is: "jonas@mydomain.com"              (new functionality)
   SpamAssassin looks for: "jonas@mydomain.com"
                           "mydomain.com"
                           "@mydomain.com"
                           "GLOBAL"
                           "@GLOBAL"

   This allows not only a per-user configuration, but also a per-domain 
   configuration with setups that use full e-mail addresses as usernames, e.g. 
   vpopmail setups.