The problem is in the "Mail" section reporting a "Fail" on both acceptance of postmaster and abuse mailboxes. parkersmaplebarn.com domain name indeed has discrete postmaster@parkersmaplebarn.com and abuse@parkersmaplebarn.com mailboxes which we have tested by sending and receiving mail to these mailboxes.

The dnsstuff.com error message is in error: "74.208.177.62 | unexpected response to [RCPT TO: abuse@parkersmaplebarn.com>] | 550 5.7.0 Your server IP address [74.115.13.4] is missing a reverse DNS entry."

It is a reporting erro because 74.115.13.4 resolves to Registrant: SolarWinds, Inc., 7171 Southwest Parkway, Building 400, TX, rather than 74.208.177.62 which does resolve to parkersmaplebarn.com which has a valid reverse DNS entry from your web site: 62.177.208.74.in-addr.arpa. PTR IN 86400 103ms parkersmaplebarn.com.