I have an 8700c which I use to check, among other things, a POP email account I have for my personal website. At home I check my email on my computers, using OSX mail, both of which are set to leave a copy of emails on the server. At work, I use a webmail program called @Mail that my host provider has set up. My problem is that my BB is deleting all the emails that are left on the server if I open an email on my BB at the same time that webmail is looking for new mail. It's really frustrating because I need to keep all my messages on the server so I can have access. Has anyone had this problem before? It's making me crazy!!

Make sure the email server itself has mail retention of a few days enabled...

It retains my mail indefinitely. Until I delete it.

My BB 8700 deletes all mail recieved on my pop yahoo.com account. I called yahoo and they said there should be a setting in the bb that says to leave a message on the server (yahoos) I can't seem to find out where that setting is.

That setting is NOT on your Blackberry. It is not on your BIS page.

That setting is routinely on your email server for your POP account, in this case, it should be on the Yahoo server.