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Create an SPF record

Posted 23rd November, 2018

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An SPF record is a DNS TXT record which includes information on how your emails should be delivered. It is used as a reference by mail recipients in order to judge the likelihood of mail being spam, or to find out whether mail should be accepted or not.

Because of the ease with which a sender can spoof an email address, there is no guarantee that the message you receive from [email protected] is actually from Dan; that could just be a faked header. And when Dan actually sends his emails not only from his own mailserver, but sends round emails from mailing software like CampaignMonitor, and from the contact form on his website, then it can be hard for a spam filter to differentiate between spam and legitimate messages.

An SPF record essentially contains two parts. The first is a set of servers from which mail is to be expected. This can include a list of IP addresses or full hostnames (see below for the full criteria). The second part is a rule on how that list should be treated: whether any messages that don't match those rules should be discarded or delivered anyway.

Some examples of SPF records are as follows:

v=spf1 ip4: -all
v=spf1 +a +mx -all

Broken down to the constituent parts:

SPF DesignationListRules
v=spf1+a +mx+all

SPF Designation is always v=spf1. This simply defines the TXT record as SPF.

In the list criteria, the options that can be added are as follows:

aThe A record of the domaina
a:domainThe A record of another
mxThe resolvable IP of the MX record of the domainmx
ipv4An IPv4 addressipv4:
ipv6An IPv6 addressipv4:1080::8:800:0000:0000
includeA domain that send

IP addresses can also be given a CIDR range, for example /24.