SPF
SPF (Sender Policy Framework) is an email authentication protocol aimed at detecting email spoofing and stopping unauthorized senders from using your domain to send emails. SPF email records maintain a list of verified senders for your domain. These records can be publicly accessed and retrieved by receiving servers to authenticate emails, as specified in RFC 7208.
What SPF Means For Your Email
SPF stands for Sender Policy Framework and was introduced in the early 2000s. Initially, SPF stood for Sender Permitted From (also known as SMTP+SPF), but in February 2004, it adopted the name we use today: Sender Policy Framework
SPF (Sender Policy Framework) allows domain owners to publish a list of authorised email servers (IP addresses or hostnames) permitted to send emails on their behalf. Here’s a step-by-step breakdown of how SPF works:
The domain owner publishes an SPF record in their domain’s DNS. This record specifies which email servers are authorised to send emails for that domain.
When an email is sent, it includes information about the sender’s domain. The recipient’s email server extracts the domain from the sender’s email address and performs a DNS lookup to retrieve the SPF record of the sender’s domain.
The SPF record contains a policy defining which servers are allowed to send emails for the domain. The recipient’s email server compares the IP address or hostname of the sending server against the authorised servers listed in the SPF record.
Based on the SPF check, the recipient’s email server determines if the email came from an authorised server. The recipient’s email server then takes action based on the SPF check result, such as accepting the email or marking it as spam.
How to Use SPF in Email
To use the SPF email standard, ensure you understand how it works and check your domain’s and email service provider’s SPF support. Then, create an SPF record, publish it on your DNS, and ideally combine your SPF DNS implementation with DKIM and DMARC to prevent spoofing.
Why is Sender Policy Framework Important for Email?
SPF ensures emails sent from your domain are genuine and not fake lures created by cyber attackers. Key benefits of SPF include reducing email spoofing by verifying the authenticity of the sending server. It improves email deliverability rates as recipient servers are more likely to accept emails from authorised servers. SPF also minimises the likelihood of legitimate emails being marked as spam, building and maintaining a positive sender reputation. Furthermore, it makes it harder for malicious actors to send fraudulent emails, helping to reduce phishing and spam. Many email service providers and organisations require the use of SPF for compliance with email standards.
How to Enable SPF Policy
To create an SPF record, first determine the authorised email servers by identifying the IP addresses or hostnames of the email servers authorised to send emails on behalf of your domain, including your own organisation’s servers or third-party service providers.
Next, define your SPF policy by specifying which servers are allowed to send emails for your domain. You can choose to allow only specific servers or include a range of servers based on IP addresses or hostnames.
Then, determine the SPF format. Publish SPF records as a TXT record in your domain’s DNS, ensuring the record is in the correct format and contains the necessary information. Access your domain’s DNS management system and add a new TXT record with your SPF record, specifying the hostname (usually “@” for the domain itself) and pasting the SPF record in the value field.
SPF Record Example
Here’s an example of an SPF record in your DNS:
v=spf1 ip4:192.168.0.0/16 -all
How to Check SPF
After adding the SPF record, it may take some time for the changes to propagate across the DNS system. Use an SPF record check tool to verify the correctness of your record and ensure it is recognised by the DNS. For complex configurations, consult your system administrator or IT support.
SPF for Third-Party Vendors
To align your third parties with SPF, include IP addresses or SPF-handling domains unique to them in your domain’s record. Avoid multiple SPF records for the same domain. For example, if using SuperEmails.net as your email sender, and their SPF-handling domain is spf.superemails.net, your SPF record might be:
v=spf1 include:spf.superemails.net -all
Limitations of SPF
While SPF protects your domain against spam and forged sender addresses, it has limitations. SPF may fail when emails are forwarded because the forwarding server may not be listed in the SPF record of the sender’s domain. Managing and maintaining SPF records grows complex as the number of authorised email servers and third-party services increases. SPF focuses on verifying the authenticity of the sending server but does not provide encryption or content verification as DKIM does. SPF only validates the sending server’s authenticity, not the specific sender, making pairing SPF with DMARC crucial.
Make SPF Even Better with Powermail
SPF alone is effective, but cybercriminals can bypass the IP address verification phase. Incorporating SPF into DMARC enhances its effectiveness and keeps your email security robust.
