You can delete messages one at a time, or select a group to delete all at once. You can also move messages from one mailbox or folder to another.
Open the message and tap
.
You can also delete a message directly from the mailbox message list by swiping left or right over the message title, then tapping Delete.

When viewing a list of messages, tap Edit, select the messages you want to delete, then tap Delete.
When viewing a message, tap
, then choose a mailbox or folder.
When viewing a list of messages, tap Edit, select the messages you want to move, then tap Move and select a mailbox or folder.