Microsoft has finally enabled TLS support in its Mail application which was missing from the Windows 8 and 8.1 versions of the app, making it a bit future-proof as more servers drop support for SSL. The IMAP standard defined TLS support all the way back in 1999. Yet, when Mail for Windows 8 and Windows Phone 8 were released back in 2012, only the now deprecated SSL method were available for encrypted communications with IMAP servers. However, Microsoft now has come in terms with STARTTLS command and starts using modern protocol encryption standards.
Mail has a strong preference for SSL over TLS and according to a report from Aeyoun, the implementation is still a bit dodgy as Windows will try to connect to the legacy port 993 (IMAP+SSL) and attempt to establish an SSL connection. Failing that it will try the same on port 143 before falling back to attempting a standard STARTTLS negotiation for TLS on port 143. Specifying the port number to 143 will remove the first attempt, but will still attempt to establish a SSL connection on that port before making another attempt for TLS.As most mail servers have been dropping support for SSL 3.0, users would have been faced with issues connecting through the Mail application on Windows. However, recent update on app in the latest Windows 10 build allows app to support TLS.
Another annoying (or may be interesting) update that Mail app for Windows 10 will have is it will not support LIST SPECIAL‐USE folders i.e. IMAP extension RFC‐6154 will not be used to configure special‐purpose folders like Trash, Junk, and Sent. Instead, Mail will use hardcoded localized folder names that may or may not match those of your other email clients. On the other hand, the new look could be refreshing!! The naming issue with the Windows 10 and 10 Mobile apps is also a bit offsetting. On Windows 10 Mobile, the app is called “Outlook Mail” but on Windows 10 it’s called simply “Mail”.
Mail for Windows 10 being new and modern app, IMAP client makes it more security oriented. Although, the change hasn’t been documented by Microsoft and made official, it will be good to see similar update in Windows 8, 8.1 and Windows Phone 8 versions of the application that will have support for TLS!! So with update to Windows 10, latest Windows app will speaks the IMAP language, but it’s clearly not going to be an inherent speaker.