The macOS Mail App is used my many Mac users. It has always had its bugs and problems, but I think it is still useable if you don’t have tons of Email. One recent problem is the Mail App crashing on its own. This necessitates a “Reboot” of the Mail App. This has not happened to me because I don’t use Mail any longer. However, if you are experiencing this issue, then read this article describing this behavior and offering several ways to fix it.