How do i stop outlook exchange deleting e-mails randomly!?

My outlook exchange [server?] appears to be randomly deleting two or three e-mails per day!
I have set up an automatic copy/forward of all e-mails received by outlook exchange so that they all appear on my googlemail account. so I can see e-mails on there that have been forwarded from my outlook exchange server but they are nowhere to be found on my desktop outlook or on my blackberry.
Has anyone else had a similar problem and/or can anyone suggest a solution please!?
Thanks