How can you delete a lot of emails from an iPad. When I try the edit/select/delete sequence the emails go but when I go back later they have all reappeared. I have been able to delete the emails from the equivalent mailbox on the iMac but this makes no difference to the iPad.
My guess is you are using an IMAP account so the boxes appear on the email server. When you delete them with your iPad, the server should comply and delete them but they often don't so they immediately get put back. If you log in to the webmail service of your email provider, you will be able to delete them there. (Your iPad will probably comply but if it doesn't, delete them there too.) It's unlikely, but if the server is really fast at synchronising, you may need to turn wi-fi off on the iPad so you can delete from both places before they synchronise again and undo your work!
Another guess is that the mailboxes on the iMac were stored in the "On My Mac" section which is as it says - on your Mac, not on the server. The server cannot see that so does not know they're gone and cannot put them back.
Lionel Ogden 