outlook 2003 automatic send receive does not receive all emails

We have 80 users using outlook 2003 with windows XP.

the outlook does not automatic send receive all emails.

When the user press the send/receive button stacks on “send/receive status ##%”.

Even at sending…

to resolve for the moment the problem, the user has to restart outlook to receive or send.

I checked all windows and office updates and all users are up to date.

This problem begun 2 weeks ago and for some users randomly. it doesn’t happen to everyone. Some users have this problem once a day, some others every 2-3 days.