Outlook has a tendancy to delete emails from the server automatically ad as you correctly pointed out, ticking the option to leave a copy is often the best way to ensure there's something there for the Blackberry service to pick up.
Try making sure this is ticked then run it for a while to note any improvement in the situation,
I am still having issues so phoned your tech support, got through to sunny Egypt and I was told......
now wait for this, its amazing technical advice .....
to turn it off and turn it on again !
Then if it didnt fix, you would replace it.
I dont know how much you pay these guys, but their advice is invaluable.
I am still having issues with the BB deleting emails. I think I might have solved it by changing the reconcile now option setting to delete on handheld, not on prompt, which is now leaving my emails on the server and for 24 hours now on my phone.
If it happens again, you can have the phone back, and I will cancel my contract.
Your tech support is now worse than BT, and thats saying something, your customer service advisors dont want to or dont have the time to help and well, after 7 years as a customer, I think either cost cutting or new staff just dont give the same commitment to their customers. I Would never dream of not ringing someone back after I promised to, no matter how busy I was, I would just stay later.
Wow, I think you almost broke my sarcasm meter!
I'm really sorry the advice you were given was not up to scratch. I will feed this back to the front-line tech teams.
You're right that turning off Wireless Reconciliation will stop the Blackberry from deleting emails from the handset which are no longer on the server - however, the fact it is doing this means that there is still something somewhere deleting your emails from your POP Server.
It can't be the Blackberry, which only leaves Outlook. I think it's worth double-checking the Advanced settings for your email account again and making doubly sure that all computers you check this account with are told to leave messages on the server after downloading, and to only delete them after a set amount of time (or when deleted from deleted items). That will put the issue to bed for you once and for all