Place a check mark to the left of the first email you want to delete, then scroll down to the last email you want to delete. Hold down the shift key, then place a check mark to the left of the last email you want to delete. This should highlight all the emails. Click on the delete. The new mail is on one continuous scrolling page, so you may have a little bit of trouble with it. It's best to just delete a few at a time.
You can switch to the basic mail and choose how many per page. That might be easier. Click the gear then click either options or switch to basic mail.
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Place a check mark to the left of the first email you want to delete, then scroll down to the last email you want to delete. Hold down the shift key, then place a check mark to the left of the last email you want to delete. This should highlight all the emails. Click on the delete. The new mail is on one continuous scrolling page, so you may have a little bit of trouble with it. It's best to just delete a few at a time.
You can switch to the basic mail and choose how many per page. That might be easier. Click the gear then click either options or switch to basic mail.