I need help in configuring HA/resilence for my dovecot (POP3/IMAP) server.

I have one RHEL Linux POP3/IMAP server with Dovecot version 2.2.10. I also installed the postfix(version: 2.6.6) in it. At present it have around 10 domains and each domain is having around 20 email boxes. It has very simple configuration.

User's reading the email via some internal applications/Outlook.

I would like to create resilience/HA for this environment. Could you please suggest me, what is the easiest way to achieve this?

If any one can suggest step by step that will be more helpful to me.  

Thanks,
Kishore