How much free memory does he have in each Blackberry? When the memory is very low, a Blackberry will delete older messages.
Here's a quote (http://www.pdastreet.com/articles/20...How-to-Do.html
) from How to Do Everything with Your BlackBerry by Curt Simmons :
"When memory begins to run low, the BlackBerry has to make room for new, incoming messages. To find the room it needs, the BlackBerry begins deleting the oldest messages in the Messages folder; however, messages stored in your Saved Messages folder are not deleted. In order to avoid the potential message loss, it is important that you keep your Messages folder tidyódelete messages you donít want and save messages that you do want. These housekeeping actions will help ensure that you do not lose e-mail that you might need."
Simmons doesn't say so here, but I seem to remember reading somewhere that it only deletes the messages you've already read.