Have you noticed that when you sign in to your Windows 8 using your Microsoft Account, apps like Messaging, Mail, People, Calendar and so on will automatically sign you in. This is for your convenience so that you do not have to sign in to each app individually.
Disable Auto Sign In Of Messaging App in Windows 8
While many find it useful, some may not want the Messaging app to sign in automatically. To disable the auto-signing of the Messaging app, open it and press Win+I to open the Settings.
Click on Option.
You will see an option to Disable or Enable All messaging services viz. Send or Receive messages. Move the slider from On to Off.
That is all!
The Messaging app will no longer sign in automatically when you sign in to your Windows 8 using your Microsoft Account.
Now you will have to manually open the app and sign in to the Messaging app should you wish to.