3 easy steps to fix Apple Mail.app keeps crashing on macOS when launched [SOLVED]

[Andy]

If you launch the Mail app on your macOS and it keeps crashing, here's the quick fix.
These three steps are very safe to do and will not harm your Mail or Mac in any way.

1. Go to ~/Library/Mail/VX/MailData using Finder or Terminal.
   Hints:
   
   • On Finder window, press Cmd+Shift+G to quickly go to the folder you want;
   • VX: Depending on your Mail app version, for example, Version 14.0 (3654.120.0.1.13) shows V8 on the file system.
2. Delete any file that begins with “Envelope Index,” such as Envelope Index or Envelope Index-shm.
   

   andy@iMac ~ % cd /Users/andy/Library/Mail/V8/MailData 
   andy@iMac MailData % ls -alh Envelope*
   -rw-r--r--@ 1 andy  staff   201M 12 Oct 10:41 Envelope Index
   -rw-r--r--@ 1 andy  staff    32K 12 Oct 07:53 Envelope Index-shm
   -rw-r--r--@ 1 andy  staff   3.5M 12 Oct 10:42 Envelope Index-wal
   -rw-r--r--@ 1 andy  staff   384K 12 Oct 07:53 Envelope Index..tmp.V6Gcqc-shm
   -rw-r--r--@ 1 andy  staff     0B 12 Oct 07:53 Envelope Index..tmp.V6Gcqc-wal
   andy@iMac MailData %

   Tips: Before you delete the files, it makes sense to copy them to a folder on your desktop.
3. Launch Mail, and the app will build new Envelope Index files -- this can take a long time if there are numerous messages to go through.

Tips: If everything seems to be working correctly, you can now delete the copies of the "Envelope Index" files from your desktop.
Thank you for stopping by this article, and I hope these 3 easy steps work for you. Feel free to post your comments or questions down below