If you haven’t changed any Mailock settings, messages you open or send are automatically replaced with unencrypted versions. If you use the reader pane in Outlook you would see the encrypted version (showing a ‘Read my message’ link), but if you double click on the message to open you’ll get the unencrypted copy, and this will replace the encrypted one in your inbox.
If you’d like it to work differently, so that your secure messages remain encrypted, you need to change the add-in settings:
Click on the 'Mailock' tab
Click on 'Add-In Settings'
There are 2 options for saving decrypted messages:
Tick if you’d like to replace your opened secure messages with unencrypted copies. Untick if you’d like to leave them encrypted
Tick if you’d like a decrypted copy of your securely sent message in your 'Sent Items'. Untick if you’d prefer to keep an encrypted copy
Click on ‘Save’ to close the Settings window.