This feature allows for personal touch when sending out first messages/questions to an included participant. Send an introduction message at the beginning of a survey to all new respondents.
You can also create an Intro Message to all participants prior to each iteration. Such Intro Message could be “Dear [X], In a short while you will receive this weeks questions. We appreciate your participation. Best regards project team [x]”
Intro messages helps making the survey more personal and could eventually maintain participants in the survey. Further this is a good idea, so the participants get familiar with the project number.