email server certificates

[Damien Hull]

Here's what I have

   1. Ubuntu 6.06 server
   2. Postfix
         1. TLS etc...
   3. Courier-IMAP
         1. Secure connection (SSL)


When I installed the packages a certificate was created for security. 
When I connect it asks about the certificate. It puts a lock icon on the 
account so I know it's secure. All was fine for the past two months or so.

The message I get when I connect says the certificate has expired. Do I 
need to worry about this? Should I create a new certificate and if so 
how do I do that?

I want secure SMTP and secure IMAP.