We'll remove messages older than 30 days to keep your inbox neat and tidy and you can't delete individual sent messages but you can remove conversations.
Here are some instructions for deleting conversation from your Inbox:
- Select the Inbox icon and jump over to your Inbox page
- Take a look at the left hand side of your conversation for those small boxes
- Select the box beside the conversation you would like to remove, and tap the little garbage can icon
- Make sure you confirm the deletion, by selecting "Ok"
Note that deleting messages is a permanent action.