Windows Live Mail and Windows 10

When I send an e-mail and then check in the sent box if it is there, I get the following message:

'Your server has unexpectedly terminated the server connection....

Your IMAP command could not be sent to the server, due to non-network errors. This could, for example, indicate a lack of memory on your system.

Configuration:
   Account: Cgfletcher.plus (friendsgreg)
   Server: imap.plus.net
   Username:
   Protocol: IMAP
   Port: 143
   Secure(SSL): 0
   Code: 800ccc0f'

Please advise what to do.

Thank you.