Many users of Windows Live Mail 2012 have received an email under this heading from the Outlook Team advising them of the changes that are taking place at Outlook.com as accounts are migrated to the same platform as that used by Office 365. Apart from advice to switch to using the built-in Mail apps on Windows 8.1 and 10, users are instructed to apply the patch KB3093594. A few points to note:

1. The change means that migrated accounts can no longer be synchronized using the old DeltaSync protocol. To synchronize these accounts, users can set up the account again to use IMAP. This will enable mail messages and folders to synchronize, but not the calendar and contacts.
    
2. The patch enables support for Exchange ActiveSync (EAS) to be used instead of DeltaSync in Windows Live Mail 2012 on Windows 7, 8 and 8.1 (see System requirements on the download page). It updates Windows Live Mail to build 16.4.3563.0918.
    
3. Users who install the patch on Windows 10 may find that the program crashes soon after start. This will only happen if the user is automatically signed in on program start, or attempts to sign in later. Some users have found that they can prevent this crash by running the program in Windows 8 compatibility mode:
    
   1. Install the patch when no programs are running. The program may open and crash - if it doesn't, close it down and wait a few minutes.
       
   2. Reboot the computer.
       
   3. Open File Explorer (Windows key  + E) and navigate to
      C:Program Files (x86)Windows LiveMail*
      and open the folder.
       
   4. Right-click on wlmail.exe and select Properties. On the Compatibility tab, select Run this program in compatibility mode for > Windows 8. 
       
   5. Click Apply and OK, then launch Windows Live Mail and test.
       
4. Mail synchronization errors can often be cleared by removing the account, closing down the program and waiting a few minutes, then re-launching it and adding the account back again.
    
5. We don't know what is going to happen with Windows Live Mail 2009 on XP and 2011 on Vista. It is clear that users will no longer be able to sign in with a migrated account to synchronize contacts and calendar, and they won't be able to synchronize mail messages and folders using DeltaSync. Whether the programs will continue to work in other respects (e.g. as a POP3, IMAP and NNTP client) remains to be seen.

* Assuming you have a 64-bit system. If yours is a 32-bit system, leave out ' (x86)' from the file path.