Mail not working on iMac with Ventura

Have a look at > If you can’t send or receive email on Mac to see if anything there helps.

If that doesn't help, log out or remover your Mail Account and re-Add it to Mac mail.

Log out of or remove email accounts in Mail on Mac

Add email accounts in Mail on Mac

In what way, exactly, is the Mail app not working?

Does it fail to launch, does it not connect to your mail servers... is there some other problem?

Does the problem with your Mail app also happen in safe mode.  Safe mode will often correct weird software behavior by forcing the OS to clear caches, do disk repair and other self-maintenance and housekeeping and temporarily disables third-party mods.

How to use safe mode on your Mac - Apple Support 

Does the problem go away in Safe mode? 

If so, this may indicate an OS software conflict with your apps.

You can exit safe mode by restarting your Mac normally, then reevaluate the problem.

Are you running any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your iMac?