It doesn't matter how fast it gets there. All that matters from
a legal standpoint is when it was mailed - hence the postmark.
The USPS copy *should* be sent by a mechanism that guarantees
tracking and proof (by the postoffice) of delivery to the correct
address. I think that's called Certified these days. Many here
recommend you don't bother with Return Receipt, since
that forces Wyndham's pickup agent to do something - and all you
really need is a record that you sent it to the correct address on
such-and-such a date. The postal clerk will show you a tracking
number you can use online to see that it got there.
https://www.usps.com/ship/insurance-extra-services.htm