Account Missing from left column

Version 7.0.26687.0 - I added three email accounts. All three show under accounts. If I start a new email, I can use any of the three accounts to send emails. However, in the left column under MAIL - where you see the Inbox, etc., for the accounts, the third email address is not showing. Any suggestions?

Are you using the Free-Version?
Only the “Pro”-Version support more than 2 Accounts…

Fritz