Help ! My machine is hacked and send junk mail to others.

[Almond Wong <almond asiaonline net>]

Hello all.

I'm using 4.1 as mail server for years. Recently, my machine is hacked.
The hacker use my machine as gateway to send junk mail.

I'm trying migrate to 6.1/6.2, please advice how to avoid this happen again.

Thanks in advance. Have a productive week.

Best regards,

Almond Wong