While there is no archive for CivicSend messages, you can prevent messages from being available to the public by assigning them an expiration date. This article will show you how to use the Message Expiration option.
Instructions
Navigate to Modules > Content > CivicSend
Follow the instructions to create a Template Message in CivicSend
Select the box next to Want Your Message to have a Public Expiration Date?
Click on the Stop Public Display on: field
Select a Message Expiration Date
Ensure that everything is correct, and select Send Now to send the message