can't import mailbox to mac mail
Problem
When I open mail, I get the message that I need to import mailboxes
When I do that 34,00 messages are downloaded
Right at the end, I get an error message saying import failed - I've done this 15/20 times
This means I can't access any actions within Apple mail
I have followed online guidance (e.g, in mail data, remove any files beginning with envelope)
I have re-installed system software
Background
For some time I have had slow apple email (e.g., no actions possible as files are being moved)
As my (1tb) disc was full, I assumed a lack of disc space and bought a 4TB external drive - no improvement
I installed Ventura on both discs and specified the new drive as start up - no improvement
So, I followed online guidance and deleted certain files
Now, on opening Mail I get the above message (import mailbox)
I've tried every suggestion I have found, but currently Apple mail is totally non functional
I can get Apple mail on iCloud and Apple and my local one on iPhone - not on my mac
Help would be appreciated
MacBook Pro 15″