I am using Office.mac 2011

We use Outlook as our default email account, the server we are currently on is a 3rd party & I want to take the domain name to 1 & 1

My main worry is that when I alter the setting for my server in Outlook from a POP 3 server to 1 & 1 which is an IMAP server will I lose my email history

OR Is the email history on my Mac saved to my folders.

I have already backed up by exporting to my Documents & also a memory stick apparently this data is stored in an OLM file which I don't believe I can access??

Thank you to anyone who can offer any assistance