People still use Banyan VINES!
Anywho, I was a network admin and we used VINES 5.54(20) then made it up to 6.3. Can't say that I remember exactly how the mail was stored or the exact options that I used to get into it from the server's console. If it helps any Beyond Mail was the 3rd party app used to give users a GUI. I'll always remember the VINES mail as being "blue mail" because of the default blue screen from dos. It was always envoked by using the mail.exe from the (Z: drive) VINES shared drive w/ all the user commands.
It wasn't too difficult (if you had the maint password) to get into the OS and read any user's email messages. It was even possible to save their attachments to one of the shared drives. This was not something that involved beyond mail.
I also remember we had a "program" floating around that someone created called "name.exe" that allowed you to change your login name to whatever you wanted (user@group@org) However it only fooled the chat.exe and send.exe programs, if you changed your name to another valid user you couldnt see their messages or send email from that name.
Well, this was just my two cents. I really enjoyed working with VINES when I had the chance, hope this helps an any way!