Yes. You can encrypt any data using this application as long as it's organized in folders. However, the product doesn't have the ability to encrypt folders that aren't stored on your computer (i.e. folders from your email account). To encrypt your mails, you first need to export them to the PC, and after that use the Okoker Encrypt Folder to encrypt the folder in which you stored the mails. There is no other method to fix your problem.
