I received the Windows Live Mail Error 0x800CCC0F following a restart after my Win7 machine shut down unexpectedly. I have numerous email accounts on Windows Live Mail which I monitor, including Gmail IMAP, Hotmail and POP. All accounts were affected. After I had logged in to Windows Live Messenger, the Hotmail account in Windows Live Mail was again working. All the other accounts gave this error (with different text according to each account):-

Unable to send or receive messages for the xxxxx Gmail account. Header download for the xxxxxxx folder did not complete.

Server Response: 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.
Server: 'imap.gmail.com'
Windows Live Mail Error ID: 0x800CCC0F
Protocol: IMAP
Port: 993
Secure(SSL): Yes

I read through all the forums for Error 0x800CCC0F and did not find a definitive answer, but I seem to have managed to solve the problem anyway. I did a repair of Windows Live Essentials through Programs and Features in control Panel, but the same issue remained. I then went through the Account Property settings of one of the affected accounts to check the information for servers and ports and authentication method etc. I noticed under the Servers tab for Incoming Mail Server, that the Password field was blank, even though the Remember password box was checked and the Username was intact. After inserting my password in the blank field and saving, the send and receive for that account worked correctly and the problem was solved. The Password field in each of the other accounts was also blank and the Remember password box was checked in each case. After going through each of the accounts and inserting the password, everything worked again.

It would appear that the unexpected shutdown had caused a corruption of the password store, which resulted in all the blank password fields. It is unfortunate that the error message was misleading and had indicated it was due to non-network errors or lack of memory. It seems as though the client was sending a blank password along with the username during authentication which had caused the error. One would have thought that sending a blank password would have resulted in a more specific authentication error.

I seem to recall with earlier clients, a blank password would result in a username and password input popup. In my opinion, in case the password field is blank, the Remember password box should be automatically cleared which would then invoke the password input popup.