Database Mail Stop Working
I certainly can't explain why any Windows patching would remove executables from your Binn folder; that sounds more like the work of "security" software or manual intervention.

In any case, there are a couple of things you can try:


run setup and try a repair against the SQL Server installation. Maybe start with just the shared components.
copy the missing files from the Binn folder of another installation that works and is the exact same edition and @@VERSION. If you don't have one of these readily available, you could probably install Evaluation Edition on your workstation or a VM. But really you should have a mirrored installation somewhere that matches production so that you can test Windows patching and any other updates there first before you "try it out" in production.