YouTube has an internal messaging system, which you can use to privately contact other YouTube users to whom you would like to send comments or meet. As you spend time conversing with other members, you may find that the size of your inbox grows to the point where you have difficulty finding older messages you want to reference. You can delete unwanted messages from your YouTube inbox to clean out the clutter and reduce your inbox to only the messages you find most important or noteworthy.
Click the envelope-shaped icon at the top of the page to view your inbox. The inbox displays a list of your new and saved YouTube private messages.
Click the check box next to the title of the message that you want to delete. You can select multiple messages to save time.
Click the "Delete" button above the inbox list to delete the selected messages.