Although conventional email programmes claim to be able to support message revocation, recipient email client settings and cross platform message delivery (to mobile devices etc) means that revocation is rarely achieved.
Mailock is able to effect true message revocation as it uses a challenge question to confirm the recipients identity before granting access to the message; regardless of the recipients email program settings or the devices being used.
A Sender is able to fully revoke a message, its content and attachments by simply setting the revoke switch in the Outlook add-in or mobile App. See the article How do I revoke a message? for details.
Even if the recipient has previously successfully opened a message, once it is revoked by the sender, any future attempts to open it will be blocked.