This is subject is clearly related to data security . In some legislations, there may be specific rules applicable to the protection of certain sensitive data, and likewise, commercially sensitive data may need to be protected, e.g. through encryption, againist unwanted leaks. There are many highly effective encryption systems available, but it is worth reminding potential users that, if the message is important enought to be transmitted in encrypted format, it is sufficiently important to be stored in that way, as long as it needs to be protected. In particular, decrypted and encrypted versions of the same message should never be stored in the same location.