Mail quits unexpectedly

I have a MacBook Pro (estimate 2012) running OS X Capitan, version 10.11.6. My Mail is vital to my work and it keeps quitting unexpectedly. Today, it quits as soon as it is launched. I have tried all suggestions I could find with those having similar issued and probably sent 10-20 Problem Reports to Apple. This problem started a few months ago when Mail would quit every time I emptied the trash and/or Junk files. Then it started quitting while I was reading an email. Today, it quits immediately after launch. Has anyone had similar problems and had them resolved. I am at a standstill until I can get this resolved. Thanks.