same email arrives late for some users but arrives on time for others

I have and Exchange 2003 server running on a Windows 2003 server.
I have several company directors involved in a very important project. Email sent from one of our lawyers to all the directors arrives on time for some of the directors, but it may late several hours for the others.
All the directors are using Windows XP, with all the patches and Outlook 2003. as usual late email puts a director in a disadvantaged or dangerous position if all the others answer and he/she does not.
I have a firewall and a filter appliance. We have checked the filter and there are no emails from the sender being held...and we know it arrived at some of the users inbox.
Any assistance is welcomed.
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TG TranIT guyCommented:
Are their mailbox size relatively the same?  Are they in the same SG and Mailbox store?
czarubahAuthor Commented:
For the directors we don't have size limits and all of them are in the same SG and Mailbox store.
czarubahAuthor Commented:
On further investigation, my assistant has made some changes to the filter appliance and it seems that although just one email is coming in, the appliance splits the mail before forwarding to the end users. that was news to me because I assumed that Exchange would make the copies. we are referring this issue to the appliance people.
Since this is no longer an Exchange problem, I guess we can close this ticket.
thank you for your help.

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