IMAP settings: Error message yet successful send/receive

I successfully set up my eM email account a few weeks ago and appear to be able to send/receive all messages.  However, each time the following pops up: Operations pane | Errors | Connecting to [my email address] failed.  IMAP.  This could be caused by incorrect settings. | Open account settings | Diagnostics | Diagnose |  Ok |. 

I get green ticks for both SMTP and IMAP and receive a test message from myself.

Any thoughts/suggestions much appreciated!

I am getting something similar with " Server says Unauthorized" however seems to be working OK just need to get rid of this annoying pop up.