Do they know how to send an email? If they do, then all they really need to know is what fields you'll be passing them (i.e. first_name, last_name, etc.). Also, they may need to know the format you want it sent out in (or what the form looks like).
If they don't know how to send an email, what are you trying to accomplish? Is this like you sending an email from your script via SMTP instead of sendmail?