Mail app on OS X 10.10 goes blank with Office 365 Account after displaying for a minute

I am having an issue viewing email on Office 365 with Mail app.

After clicking on the Office 365 mailbox to read the emails the message list goes blank after about a minute, I then have to click on another mailbox then back to the Office 365 one to view the messages again but you only get about a minute until it does it again. This is frustrating when you are reading a long email.

This only happens with Office 365 accounts, I also use iCloud and Google mail accounts without any problems in Mail.

I have run connection doctor but it says everything is ok.

Has anyone any ideas? Or come across this before?