Receiving emails on an iPhone can be a convenient and helpful feature of the phone. Emails can build up, however, and take up quite a bit of memory on your phone if you don't delete them. Even after you send an email to the trash can, it should still be deleted from the trash can to be completely removed from your iPhone.
1.Click on the mail icon on your iPhone's homepage. The icon is blue with a photo of an envelope on it, and can be found on the first page by default.
2.Click on the name of an email account. If you have multiple accounts linked to your iPhone, go to "Mailboxes" and then select one account.
3.Tap the "Trash" icon.
4.Click the "Edit" icon in the top-right corner of the screen, above the list of trashed items.
5.Choose "Delete All" from the bottom of the screen.
6.Repeat steps 2 to 5 to empty the trash cans for your other email accounts, if desired.