A measure of similarity between an identifier of a sender of the message and each identifier of one or more identifiers of each trusted contact of a plurality of trusted contacts of a recipient of the message is determined. In the event the sender of the message is not any of the trusted contacts but at least one of the measure of similarity between the identifier of the sender of the message and a selected identifier of a selected trusted contact of the plurality of trusted contacts meets a threshold, the message is modified, if applicable, to alter content of a data field that includes an identification of the sender of the message. The data field is one of a plurality of data fields included in a header of the message.