Great idea! Your email recipients can, of course, click Reply on your email and respond to your RSVP email address. (This address is set on your Settings & Billing page or when on the Send page of your mailing.) But you can also link text to an email address within your mailing.
Highlight the text you want to link, and click the link icon in the formatting toolbar. In the popup modal, click "Email address."
You'll type in the email address and add text to the Subject field so that the subject link automatically fills in for the emailer. Text in the "Link name" field is what will appear in your Response section. Text in the "Tooltip" field is what will appear for most folks when they hover over the link. (Not all email programs support this.)