Apple Mail

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

Download and run Etrecheck. Be sure to give it Full Disk access before running.

Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to paste the report in your reply.

Then we can evaluate the report to see if we can determine the cause of the problem.

Ok, thank you. Give the following a try:

1. Open the Mail app.
2. From the app's menubar, select: Mail > Preferences > Accounts
3. Select each account, one-at-a-time, and disable it.
4. Shutdown the app, and then, open it back up.
5. Now go back to the Accounts tab, and re-enable one of those accounts.
6. Use the Mail app, as usual, for at least a day. If it crashes within that period, you most likely found the account that is the culprit. If it doesn't crash within that period, re-enable another account.
7. Keep adding back accounts until one of them crashes the app.

Please post back your results.

Are you saying that you are using the Apple Mail app and that it closes unexpectedly? If so, does it happen immediately after opening the app, or randomly while using it? How many email accounts do you have configured with it?