Bazzy
If you were to set up another administrator account on one of your laptops, you could sign into your email on that mirror account.
Let the system download all of your emails and see if the log files travel with it.
If they don’t then a non technical solution might be to use the new admin account as your primary, the apps will be there by default, sign into iCloud , import your files, the lot.
When you are confident that this new account is the old you, minus the log files, delete the account that has a massive log file issue.
I suspect some of the beach ball issue is Mail having to open a stupendously large file, add a line and then close it.
Just a thought.
If you were to set up another administrator account on one of your laptops, you could sign into your email on that mirror account.
Let the system download all of your emails and see if the log files travel with it.
If they don’t then a non technical solution might be to use the new admin account as your primary, the apps will be there by default, sign into iCloud , import your files, the lot.
When you are confident that this new account is the old you, minus the log files, delete the account that has a massive log file issue.
I suspect some of the beach ball issue is Mail having to open a stupendously large file, add a line and then close it.
Just a thought.