Problems receiving email

[Erin]

I work at a company with about 8 other people and we all
use the same email address through Outlook on 9 different
computers. However, some receive all the email all the
time, while others only receive some email some of the
time.
(I have already tried deleting the accounts individually
and then adding them back on and that did not work. I also
tried checking everyone's "Keep a copy of message(s) on
server" box under the Advanced tab when looking at an
individual email account).
Any ideas??? I'm stumped.

Thanks!
Erin