Postfix and reading mail

Hey all.

I installed Postfix and added users on my system associated with each of the email accounts that I wanted to host. I then sent an email from an outside address expecting postfix to take care of it when it arrived to the server. But when I used the 'mail' command as one of the users that I created, I was presented with:

/var/spool/mail/user1: Permission denied

If I'm logged in as that user, why would I not have permissions to view that area. Also, can I check mail on command line for a user that I'm not logged in as?

thanks again!