What is the RSVP Option?
The RSVP Option allows you to request RSVP responses from the reciptients of your message.

After they hear your message, they will be told that their RSVP is requested. They will be asked to press 1 for "yes", 2 for "no" or 3 for "not sure".

You will then be able to go to the My Phonevites page and see the individual RSVP responses in the Call Detail Record, under the corresponding Phonevite.
What is the Message-Back Option?
The Message-back Option allows recipients of the calls to leave a message back for you to hear.

After they hear your message and RSVP, if requested, they will be told that they can leave a Message-back for you.

If they leave a message, you will be able to hear it in the corresponding Phonevite details in the My Phonevites page.
Can I request both the RSVP and Message-Back Option for the outgoing message?

Simply click on both the RSVP and Message-back options.
The recipient will be prompted first for their RSVP, followed by the Message-back option.