Comparing Email servers

Currently I use Kerio and there are tonnes of problems.

1) The mail server (linux based) downs once a day (almost)
2) There are constantly virus mails, or reports of virus everyday. Sometimes it is one staff sending to another (of course he didn’t, it’s from the mail server itself). We installed office scan and it doesn’t help seems.
3) Tonnes of advertising emails everyday. Mostly about cheap software.

Is there a better mail server or virus detection tools? Any recommendation of a perfect combination? Better be low cost of course..

==================
http://pccm.blogspot.com
A typical Hong Konger sees a dim future ahead. That’s why I am working
harder to gain an edge under this adverse circumstance.