I need to log into apple mail to read new messages received from outlook
There is no interference with having more than one program retrieve IMAP mail. 

Just quit Apple Mail and don't launch it while you work out whatever is not happy within Outlook. 

Then your server will only see the requests from Outlook and you can focus on troubleshooting that setup. If you want to ask a second question on how to troubleshoot Outlook - just list your relevant details (version, etc) and document which troubleshooting article you are following from the Office support website (it's quite good in most instances) and you'll probable get some expert help.