Automatic email forwarding to a contact

Hello,

I use Thunderbird and I receive emails from contact 1, which I would like to forward automatically to another contact 2 without making any particular manipulation. The problem is that I initially had my email for contact 1 before contact 2 had an address. Now that contact 2 has an email address, I would like to stop receiving emails from contact 1 and have them forwarded automatically to contact 2.
Is there a way to configure the email client to automatically forward emails from contact 1 to contact 2?

Thank you for any help you can provide.

Configuration: Windows Vista Internet Explorer 7.0