A method of creating an annotation to an email. The method includes: receiving an email; receiving a predefined user input; creating an annotation in response to the predefined user input, the annotation linked to the email; receiving a further user input; and defining a permission for the annotation according to the further user input, the permission defining user access to the annotation. When transmitting a second email as a response to the received email, the second email is linked to the annotation. The method further includes displaying at least a part of the annotation linked to the received email, for example when a user hovers over the email. The structure of the annotations allows the associating of the annotation with one or more further annotations.