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This is my fault. I'm sorry. https://twitter.com/clairernovotny/status/1287850874518351877
Yeah I went and validated it to make sure, found in a spec I wrote August 29, 2001. Definitely my fault.
Short summary: To only have one text editor in Microsoft Office, the decision was made to have Word be Outlook's default text editor in Outlook 2003 (seen above as its code name, http://Outlook.NET ).
All of the legacy MS mail programs used Ctrl+Enter to send mail. All were being discontinued in favor of Outlook as the "one unified mail program."
Word, when used as Outlook's editor, changed the "send email" shortcut to Alt+S, because Word used Ctrl+Enter for something else.
Word, when used as Outlook's editor, changed the "send email" shortcut to Alt+S, because Word used Ctrl+Enter for something else.
I was barely out of college and I really liked the feeling of hitting Ctrl+Enter to send a mail. It was very viscerally satisfying. Ker-chung! 
But the plan was to unify everything around Alt+S as the permanent "send email" shortcut key forevermore.
But the plan was to unify everything around Alt+S as the permanent "send email" shortcut key forevermore.
So I arranged to get that UI work transferred to me and I wrote the spec and included doing extra dev work to override Word's internal code and bring Ctrl+Enter back to prominence, where it has remained for the last 20 years, now copied into dozens of other apps. I'm sorry.
