I had a huge problem deleting emails in All Mails/Archive box. You can not get rid of the box as it's Gmail's default. I tried deleting the email, but moving them to Trash kept duplicating No. of emails in All Mail Archive and I was running out of space in my MacBook (for whatever reason).
That's how I figured it out:
1. You can delete the emails from the All Mail Box within Gmail account (Gmail.com) . But you will LOOSE ALL EMAILS. Yes that happened to me. (Read further as I could have my emails back.)
2. Disable your Gmail Account in your Email App on the Mac. Export the emails to a folder in your Mac.Try deleting the emails inside the All Mail, then Empty the trash, then Enable the account back. So it will not falling in the loop and duplicating number of emails in All Mail box. I have not tried this as I deleted them from Gmail, although I disabled the Gmail on Mac, so it was not refreshed from the main server and I could save my emails.
Here is why I decided to write in here:
I had exported my Gmails to a folder on my Mac. But couldn't retrieve them back to my main Gmail (Gmail.com).
I called Apple support, they referred me to Google. Google told me as these two are competitors, I will NOT be able to retrieve the lost emails. Only way is if they (remote)install a Software on my laptop, and by using that they can use the Back up on Mac to the Main Gmail account, and that would cost me $199!!!!
Thi is not a joke, that's exactly what he told me. Of course I hung up!
What you can do:
You can Import the exported emails back to your Mac Mail.
Once you got the folder in your list, you can open and select emails and move them like any normal email to other folders, including the GMAIL!!!
The 640 is the number of my old/lost email that's back now, plus it's accessible from Google.com without a need to pay a penny!
Remember that Drag n Drop to iCloud folder is always another option to move and share emails.
Good Luck and be safe from the fools!