Email Issues - need help!

Please help, my system administrator that normally does this is sick and our virtual server doesn't seem to be sending emails for 2 days now.

It appears that mail is getting delivered to the server, but the server isn't forwarding them to the mailboxes.

I looked into all the web interface screens and frankly don't know what to look for. Can I reboot the server, If i do will emails get lost or do I need to access a log file from a command prompt on the server?