UTM tagging requires that specially formatted variables be added at the end of a standard URL. The end of the URL and the beginning of the UTM tagging begins with a ? character.
It is imporant to note that most links coming from ReSci emails are automatically appended with ?rsoid information as part of our standard link tracking. Because of that you do not need to use ? for most UTM tagging, and can use & to begin your UTM parameters instead.
Learn more here: Constructing URL Variables to Pass Data from Email