Herein is disclosed a method of verifying the authenticity of emails sent from a first email application of a sender to a second email application of a recipient, the emails each having a sender's email address, a receiver's email address, and a user accessible field for receiving content. The content of the user accessible field is visible to the recipient upon opening an email inbox in the second email application. The method includes the steps of first identifying the receiver for an email to be sent by the sender. A current sequence marker for the receiver is then generated. The current sequence marker represents a next sequence identifier in a sequence of emails between the sender and the receiver. The current sequence marker is then inserted into the user-accessible field of the email and the email is then sent.