Can I reinstall Mail in Sierra?

I have a couple of problems with Mail that manifested for the first time about a month ago.  I have posted about both but have not made any progress.  I have lost some draft messages, which just open as a blank email.  I also have trouble with the text failing to wrap on some messages.

I have tried rebuilding all the boxes and deleting the folder

/Users/donald/Library/Mail/V4

I have also triggered the maintenance scripts

My question now is whether it might be possible to reinstall the mail app and if so what is the best way to do it?

Thanks in advance,