Sender Policy Framework or SPF is an email validation system designed to prevent email spam by detecting email spoofing, a common vulnerability, by verifying sender IP addresses. SPF allows administrators to specify which hosts are allowed to send mail from a given domain by creating a specific SPF record (or TXT record) in the Domain Name System (DNS). Mail exchangers use the DNS to check that mail from a given domain is being sent by a host sanctioned by that domain's administrators.
If your domain already has SPF defined for the domain, you MUST add the following string to your existing SPF record to include our server IPs:
If your domain has SPF and not including our IPs, emails to Gmail and other addresses could fail. To setup SPF to just include our IPs, you can setup your domain SPF as:
v=spf1 include:dnsexit.com ~all
To find out what is the current SPF for your domain, you can open a DOS/Linux prompt and use the "nslookup" command. For example, to find out what is the SPF for google.com, you can use command
C:> nslookup -type=TXT google.com
google.com text = "v=spf1 include:_spf.google.com ip4:220.127.116.11/31 ip4:18.104.22.168/31 ~all"