iMac Mail app syncing issues with connection doctor for 1 year now

Last one year none from apple community, apple support, feedback app or anyone supporting.

Have iCloud custom email domain for 2 years now

Tried migrating gmail to mail app on my imac

Its been 1 years+ now with 1 gbps internet speed

Still only 62.51 gb on iCloud mail but local iMac mail has 42 gb not getting uploaded

Connection doctor shows all mails keep uploading uploading uploading for more than 1 year now.

Help me upload all emails form mail app to iCloud mail, so I could complete rest of the backup close to 1000 gb from gmail having 1,65,000 emails to be moved to iCloud mail.

Question : * check attached image for reference *

1) How to move all mails from mail app to iCloud mail

2) How to get rid of mail form flagged folder and recovered on my Mac folder to iCloud mail

3) How to ensure connection doctor is not always running non stop

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