administrator permissions mail server

Hi everyone,

I am sorry if this is not the exact forum to post this question but seemed the most relevant.
I am working in a network with 40/50 PC's managed by 3 people with administrator passwords.
The OS used is GNU/Linux.
There is also a webmail service provided by the same server, which is also maintained
by the same people.
My question is the following:
Since the administrator has of course access to all user files, does this mean that
one with administrator privileges can read everybody's emails?

Cheers,
step0ut