How can I stop Mac Mail from importing all my old emails

Drowning, not waving ... I haven't been able to open my MacMail on my iMac (late 2015 Monterey 12.7.6) since I last restarted it. It says "Importing 178,000 emails" for a while and then crashes. I either have to go online or use another device to check my mail.

Should I use a different email program?

Is there a way to trash all of the old emails at once?

Should I reinstall MacMail?

Should I upgrade to OS Sonoma?

Should I downgrade to an older OS?