Project Date is the length of time the project will run. Envelopes cannot be sent outside of the start and end dates of the project. E.g. Black Friday is only 5 days long and you want the project to end on day 5.
Envelope Expiration: The envelope expiration can extend beyond the project expiration date. You determine how long the recipient has to open and claim the envelope. Envelopes that are not claimed will expire.
