No Emails are are shown in folders or loading on start up - at all! But calender is?

Upon start up, I have a completely blank set of folders, and all my emails are lost or missing?! But for some reason my calender is still with my meeting etc?

Is there some way of finding out why no emails are showing at all? Is there something missing as to why EM Client is not being directed to my BTinternet account?

Can someone please let me know how I can get my emails back? HELP!

Many thanks,