Redtail recommends that you create a Sender Policy Framework record, commonly referred to as an SPF record for your domain. An SPF record is a type of record attached to your domain that identifies which mail servers are permitted to send email on behalf of your domain. The creation of an SPF String would be made at the domain host level. Some common domain hosts are GoDaddy, Network Solutions, 1and1, and Emerald.
The purpose of an SPF record is to discourage spammers from attempting to send messages with forged "From" addresses at your domain. This process is generally referred to Spoofing. Recipient mail servers can refer to the SPF record to determine whether a message purporting to be from your domain is coming from an authorized mail server for your email address.
For example, suppose that your domain example.com is hosted by Redtail Technology. You create an SPF record that identifies Redtail’s mail servers as the authorized mail servers for your domain. When a recipient's mail server receives a message from email@example.com, it can check the SPF record for example.com to determine whether it is a valid message. If the message comes from a server other than Redtail’s mail servers listed in the SPF record, the recipient's mail server can reject it as spam.
There are two common variations of the SPF String you can utilize based on your security and/or compliance guidance.
Redtail SPF String Value With Soft fail: v=spf1 ip4:18.104.22.168/27 ip4:22.214.171.124/27 ~all
In the above example, the tilde "~" in front of "all" means that any servers not listed in this SPF record should be treated as a "softfail", ie. mail can be allowed through but should be tagged as spam or suspicious.
Redtail SPF String Value With Hard fail: v=spf1 ip4:126.96.36.199/27 ip4:188.8.131.52/27 -all
In the above example, the minus "-" in front of the "all" means that any senders not listed in this SPF Record should be treated as a "hardfail", ie. they are unauthorized and emails from them should be discarded.
For instructions on adding an SPF String within GoDaddy.com, click here.