If the mobile policy of your organization permits it, you can add attachments to the compose screen of a secure message. You can add images from your phone or from the camera and add files from local storage or from cloud apps such as Google Drive, Dropbox, or OneDrive.
Note: Dropbox provides a link to the file instead of actual file.
To add a file device storage or cloud storage to a secure message:
The mobile policy of your organization from which you received a secure message determines whether you can add an attachment after you decrypt it. For security purpose, the mobile policy of your organization may restrict adding an attachment to specific domains.