It's a blue app with a white, sealed envelope icon.

If it doesn't open on the "Mailboxes" screen, tap Mailboxes in the upper-left corner of the screen.
 It's next to a blue trash can icon., It's in the upper-right corner of the screen., It's in the lower-right corner of the screen., All of the deleted emails from the Mail app, with all of their attachments, have now been deleted from your device., It's in the upper-left corner of the screen., It's next to a blue dumpster icon that contains an "x.", It's in the upper-right corner of the screen., It's in the lower-right corner of the screen., All of the junk emails from the Mail app, with all of their attachments, have now been deleted from your device.

If you use an alternative mail client, such as the Gmail app, go through the processes specific to the app to remove deleted and junk emails.
Open the Mail app.
Tap Trash.
Tap Edit.
Tap Delete All.
Tap Delete All.
Tap Mailboxes.
Tap Junk.
Tap Edit.
Tap Delete All.
Tap Delete All.
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