Define your SPF record—Advanced setup

Who this article is for

This article is for IT professionals and people who have experience setting up email servers. It has technical information about Sender Policy Framework (SPF), including SPF record requirements, SPF record syntax, and how SPF affects email delivery. For a basic SPF record for sending email with Google Workspace only, or for Google Workspace plus your other email senders, follow the instructions in Define your SPF record—Basic setup. 

Tip: If you send email with Google Workspace only, get your SPF record in Define your SPF record—Basic setup.

An SPF record defines the mail servers and domains that are allowed to send email on behalf of your domain. It also tells receiving servers what to do with messages after they’re checked. Receiving servers check your SPF record to verify that incoming messages that appear to be from your organization are sent from servers authorized by you. Domains can have one SPF record. However, the SPF record for a domain can specify multiple servers and third parties that are allowed to send email for the domain.

 

Set up SPF

Set up SPF by adding a DNS TXT record at your domain provider.

SPF record format

An SPF record is a line of plain text that includes a list of tags and values. The tags are called mechanisms. The values are typically IP addresses and domain names.

An SPF record is added to your domain provider in the form of a DNS TXT record. Learn more About DNS TXT records.

SPF records can have up to 255 characters. The TXT record file size should be no larger than 512 bytes.

SPF record mechanisms

Use the mechanisms in this table to create your SPF record. Receiving mail servers check messages against mechanisms in the order they are listed in the SPF record.

Keep in mind:

• You can use optional SPF record qualifiers with mechanisms. 
• Your TXT record for SPF shouldn’t include more than 10 references to other domains or servers.  These references are called lookups. Learn more in Check the DNS lookups in your SPF record.

Mechanism	Description and allowed values
v	SPF version. This tag is required, and must be the first tag in the record. This mechanism must be: v=spf1
ip4	Authorize mail servers by IPv4 address or address range. The value must be an IPv4 address or range in standard format, for example: ip4:192.168.0.1 or ip4:192.0.2.0/24
ip6	Authorize mail servers by IPv6 address or address range. The value must be an IPv6 address or range in standard format, for example: ip6:3FFE:0000:0000:0001:0200:F8FF:FE75:50DF or ip6:2001:db8:1234::/48
a	Authorize mail servers by domain name, for example: a:solarmora.com
mx	Authorize one or more mail servers by domain MX record, for example: mx:mail.solarmora.com If this mechanism isn't in your SPF record, the default value is the MX records of the domain where the SPF record is used.
include	Authorize third-party email senders by domain, for example: include:servers.mail.net
all	Specifies that all incoming messages match. We recommend you always include this mechanism in your SPF record. This must be the last mechanism in the SPF record. Any mechanism that comes after the all mechanism in an SPF record is ignored. Should I use ~all or -all? When an SPF record includes ~all (softfail qualifier), receiving servers typically accept messages from senders that aren't in your SPF record, but mark them as suspicious. When an SPF record includes -all (fail qualifier), receiving servers may reject messages from senders that aren't in your SPF record. If your SPF record isn’t set up correctly, the fail qualifier might cause more messages from your domain to be sent to spam. Tip: To prevent spoofing of domains that don’t send email, use this as the SPF record for the domain:  vspf1 ~all

SPF record qualifiers

A qualifier is an optional prefix you can add to any mechanism in your SPF record. Qualifiers tell the receiving mail server whether to consider a message authenticated when there's a match with a mechanism value, for example:

v=spf1 include:_spf.google.com -all

In this example, the SPF record authorizes only Google Workspace to send emails for your domain. The all mechanism has a fail qualifier ( - ), so messages from any other senders fail the SPF check and may be rejected by the receiving server.

Mechanisms are checked in the order they occur in the SPF record. If a mechanism doesn’t have a qualifier and there’s a match, the default action is pass authentication. When there's no mechanism match, the action default is neutral: the message doesn't pass or fail authentication.

Use these optional qualifiers to tell receiving mail servers how to handle messages that match mechanisms in the SPF record.

Qualifier	Action receiving server takes with a match
+	Passes authentication. The server with matching IP address is authorized to send for your domain. Messages are authenticated. This is the default action when the mechanism doesn’t use a qualifier.
-	Fails authentication. The server with matching IP address is not authorized to send for the domain. The SPF record doesn’t include the sending server IP address or domain so messages won’t pass authentication.
~	Softfails authentication. It's unlikely that the server with matching IP address is authorized to send for the domain. The receiving server will typically accept the message but mark it as suspicious.
?	Neutral. Neither passes nor fails authentication. The SPF record doesn’t explicitly state that the IP address is authorized to send for the domain. SPF records with neutral results often use ?all

Next steps

After you’ve created the SPF record for your domain, add your SPF record at your domain provider.