You can copy-and-paste/write you email on these websites convertcase.net or professionalediting.org and click "sentence case"
You don't have to install any extensions and it's accessible anywhere as long as you are online. It's a pretty lazy way to meet your purpose.
First let us express our condolences for your loss.
Outlook.com, Hotmail, Live, and MSN email accounts are dealt with on one website.
Microsoft recently changed their website invalidating older links. Currently the information is available at: "Next-of-kin process for Outlook.com" (previously available at http://windows.microsoft.com/en-us/outlook/next-of-...