Utility messages inform customers about ongoing transactions. Such as post-purchase notification or billing statement etc. Whereas, through authentication, businesses authenticate users through one-time passwords. Those who do not come under conversion utility or authentication are classified as marketing. This includes promotions, offers and invitations. Utility messages inform customers about ongoing transactions. Such as post-purchase notification or billing statement etc. Whereas, through authentication, businesses authenticate users through one-time passwords. Those who do not come under conversion utility or authentication are classified as marketing. This includes promotions, offers and invitations.