Mac mail question

Hello everyone. This is my first post here so I best make it good right?

Anyways, my problem is with mac mail. I have two macs (a macbook pro 10.5.8, and an imac 10.6). One is at work and the other I use for home. When I try using mac mail on one I can receive all of my messages when I sign in. However, when I go to the other computer and open up mac mail with the same account, the messages that I could view on the one computer dont show up on the other. What is the problem here? How do I sync the two mailboxes to show all of my messages whether I am at work or not? Thanks in advance.

 

both account are gmail accounts. How do I fix this while using them?