Just setup Win7 and EM for my Outlook.com email and the new IMAP protocol. EM works fine logging on and fetching mail, sending and seems to work great except it will not mark the mail on Server either read or purge deleted mail using EM. Other IMAP Client on phone works fine in this respect.
so your only issue is not having emails marked properly?
Anyway I will need your IMAP log, Tools - Settings - Advanced, check IMAP under your account, apply and restart eM Client.
they try to follow same steps that leads to your issue and hit “send and receive”, after this send logs… to firstname.lastname@example.org together with this topic’s URL in subject.
after this you can turn logging off.