Migrated from Macbook Air running Mojave, Mail version 12.4. to Macbook Air running Sequoia, Mail version 16.0. Opening mail pops up a window with the message "updating mail database" - this disappears, app doesn't open.
Hi, I have exactly the same issue - I'm glad to hear you found a solution somewhere on "Apple Discussions" (where is that?) but could you please also paste a link here to the specific discussion for others to use?