I badly need to get some antispam in place on my mail server (I'm using QMail and Courier IMAP).

I've installed Spam Assassin but can't get the deamon to start - this is what happens:

spamd start
Could not create INET socket on Address already in use (IO::Socket::INET: Address already in use)
How can I view the process that's using port 783 and kill it, or make spamd run using an alternative port?