Sender Policy Framework [ SPF ] set up

use it for email verification from mail server like gmail.

before
==>
Received-SPF: neutral (google.com: xxx.xxx.xxx.xxx is neither permitted nor denied by best guess record for domain of donot-reply@xxx.com) client-ip=xxx.xxx.xxx.xxx;

after add dns txt record
==>
v=spf1 a mx -all

==>
Received-SPF: pass (google.com: domain of donot-reply@XXXX.com designates xxx.xxx.xxx.xxx as permitted sender) client-ip=xxx.xxx.xxx.xxx;

http://www.openspf.org/Introduction