In a message processing device processing a message to be sent from a sender to a user, an acceptor accepts a draft message generated by each of a plurality of senders. A registrant registers, in a database, a parts element satisfying a predetermined requirement from among elements included in the accepted draft message. A specifier specifies a non-parts element not satisfying the requirement from among elements included in the accepted draft message generated by a first sender. A display image generator generates a display image by applying a predetermined drawing engine to the specified non-parts element. A comparison image generator generates a comparison image by applying the drawing engine to an element acquired by expanding the registered parts element. A calculator calculates a degree of similarity between the generated display image and the generated comparison image. A suggester transmits, to the first sender, information prompting replacement of the non-parts element with the parts element related to the comparison image when the calculated degree of similarity exceeds a reference value.