E-mail Error Message

I have my DreamHost e-mail set up in Mac mail on my iBook G4. My e-mail works fine on my old external 300GB hard drive, but when I installed a new system on the new internal HD for my iBook, I’m getting this error message:

Unable to verify SSL server mail.vjandrews.com

Mail was unable to verify the identity of this server, which has a certificate issued to “*.mail.dreamhost.com”. The error was:

There is no root certificate for this server.

You might be connecting to a computer that is pretending to be “mail.vjandrews.com”, and putting your confidential information at risk. Would you like to continue anyway?

What does this mean? And how do I fix this problem?

– vja4Him