Yes, messages do expire. To protect the sensitive nature of your messages, the DataMotion system stamps each message you send with an expiration date. By default, SENT messages expire after 30 days. The DEFAULT maximum expiration period of your sent messages can be extended to 2 or more years. Increasing your default expiration period will cause your mailbox to fill up quicker. There is also the option to change the expiration period on a PER message basis.
After a message has expired, the contents and any attachments associated with that message will no longer be available. Metadata of the message will still be available forever in the form of message tracking and reporting.