If you TRULY want to protect your mailboxes from malicious (viruses and spam) incoming emails, you should take a look at Comodo Antispam Gateway. You will find that Comodo Antispam Gateway is very modest with its pricing.
My personal opinion is that personal antispams installed locally in the PC are a waste of resources and of time. Because the spam/virus will always reach your mailbox. With Comodo Antispam Gateway, the malicious incoming mails will not reach your mailbox. Thats what we all are looking for, arent we?