SPF stands for Sender Policy Framework. Pretty much it is a basic form of email validation that can be done to check on incoming mail. To understand this a little bit better let us identify some email basics.
When you receive an email it come from a specific email address. Let’s say you received an email from:
The sending domain is:
Another thing to note is when you receive an email it is being sent from a server that is assigned an IP address. In our example, let us say the ip is:
Now iamawesome.com wants to implement SPF to their sending domain in order to pass in servers that will check for SPF. In other words, I want receiving email servers to know that the email I am sending did come from 54.143.342.123. This is simply done with the proper DNS record. For iamawesome.com to implement this they just need to create a TXT record:
iamawesome.com. IN TXT “v=spf1 ip4:54.143.342.123 a -all”
If a receiving server checks for SPF it will see review the SPF record. The server will see that it specifies 54.143.342.123 as a sending server. It will then confirm if it did in fact receive that email from that IP. If it passes you will see in the header of your email something to this effect:
This is what you want! Pass is good!
There is a good chance the same sending domain would be used to send from multiple IPs. SPF can handle multiple entries:
iamawesome.com. IN TXT “v=spf1 ip4:54.143.342.123 ip4:22.214.171.124 a -all”
Instead of an IP address you can also put in an MX record:
iamawesome.com. IN TXT “v=spf1 mx:mail.iamawesome.com a -all”
The IP of this domain will be checked.
Another common entry is to specify a domain. If you use a domain the TXT record for that domain will be checked for SPF entries:
iamawesome.com. IN TXT “v=spf1 a:spf.iamawesome.com a -all”
This is common when you have multiple servers you are sending from. You put in multiple domains. With each domain could be multiple IPs or more domains for the server to check. However, you will want to be careful as some servers put a cap as to how many DNS queries they do to check for SPF. If you put a domain a DNS query has to be done to check the TXT record. At that level of there are MX records or more domains additional DNS queries will need to be made until it finds the information it is looking for. It is common for receiving servers to cap this at 10 DNS queries.
Is SPF important?
SPF is important, especially if you are doing bulk sends like email campaigns. There really is no reason not to add SPF to your sending domain. It’s a simple entry that you just need to add to help in getting to the inbox.