How to Delete Mailboxes in an iPhone 4by KR KnowlinUpdated September 28, 2017
The iPhone 4 Mail application lets you access the mailbox of any email account you have set up on the device. This makes it easy to check your inboxes and send messages when you're in transit. You can have multiple mailboxes set up on your iPhone 4 for added convenience. Delete an email account from the iPhone 4 to remove its mailbox from your device.
Tap the "Settings" icon.
Select "Mail, Contacts, Calendars" from the Settings menu. A new screen loads.
Select the mailbox you want to delete from the "Accounts" section of the "Mail, Contacts, Calendars" page.
Tap the "Delete Account" button at the bottom of the page that appears. Tap the "Delete Account" button again when the confirmation prompt opens to delete the mailbox.