You would be surprised to know that as many as 3.4 billion emails are sent by threat actors every single day around the globe to gain illegitimate access to sensitive user data. That’s precisely why email authentication plays a significant role in safeguarding your business email communications by securing your domain from phishing and spoofing attacks.
One of the oldest and most commonly used email authentication protocols, Sender Policy Framework or SPF, helps secure your business reputation by specifying which particular mail servers are authorized to send out emails on behalf of your domain. SPF comes with two distinct mechanisms– soft fail and hard fail.

This article aims to explore these two failure mechanisms, understand their differences closely, and thereby help you decide which one is best suited for your domain.
What does SPF soft fail do?
When a domain owner chooses the soft fail mechanism, it instructs the recipient’s email server to consider the unauthorized email as potentially suspicious. Such emails aren’t straightaway rejected; rather, they are treated with caution and then moved to spam folders.
It can be considered a forgiving mode that gives ample flexibility to domain owners who are in their initial stage of developing a fool-proof email authentication system.
A domain owner can opt for the SPF soft fail mechanism when:
- They have just started their email authentication journey and wish to avoid any kind of email deliverability issues.

- They are unsure if they have added all the sending sources to the SPF record.
- Their IP range is dynamic, which means it keeps changing, and they can’t possibly add all of them to their SPF record.
The soft fail mechanism enables domain owners to warn recipient servers about potentially unauthorized emails while minimizing disruptions to legitimate email traffic.
SPF soft fail example
Below-mentioned is an example of an SPF soft fail mechanism:
v=spf1 include:spf.example.outlook.com ~all
What does SPF hard fail do?
A hard fail mechanism is strict in nature. It stringently instructs the receiving email servers to straightaway reject unauthorized emails that are coming from servers not enlisted in the SPF record.

Domain owners who have well-established and tried and tested SPF records should use the hard fail mechanism. By implementing SPF hard fail, domain owners ensure that unauthorized emails are completely blocked, thereby significantly minimizing the risk of phishing and spoofing attacks.
SPF hard fail requires vigilant implementation. Otherwise even the slightest misconfiguration can lead to genuine emails getting rejected.
A domain owner can opt for the SPF hard fail mechanism when:
- Their SPF record is carefully validated and tested across all email-sending sources.
- They wish to get stricter control over their business’ email authentication system.
SPF hard fail example
Below-mentioned is an example of the SPF hard fail mechanism:
v=spf1 include:spf.example.outlook.com -all

Which SPF failure mode should you use for your domain?
In order to implement the suitable SPF failure mechanism for your domain, you must clearly understand your domain needs, email infrastructure, and the SPF implementation stage.
As a domain owner, you must use SPF soft fail when you’re considerably new to SPF implementation. It helps those domain owners who are still in the process of identifying legitimate email-sending servers. A soft fail mechanism is also suitable for domains that rely on third-party email services and may require adjustments to your SPF record. It also helps domains with seamless email delivery for legitimate emails during the initial implementation phase of the SPF protocol.

The SPF soft fail mechanism is ideal for domain owners looking for a balanced approach. It enables domain owners to test their SPF strategy without experiencing any kind of email delivery failures.
The hard fail mechanism is used by domain owners who already have an established SPF record and are crystal clear about all the email-sending sources from their domain. Also, domains that require an extra layer of protection, such as the ones associated with government sectors and the finance industry, should go for a strict hard fail mechanism to ensure enhanced security.
The best way out is to initially start with soft fail and then further move to hard fail once you are confident about your SPF record configuration. This gradual phasing approach minimizes the element of risk as well as enhances the smooth deliverability of legitimate emails.

SPF is a powerful protocol that helps safeguard your domain from any kind of email-based attacks. As a domain owner, you’re required to make the appropriate choice- soft fail or hard fail- to secure your email communication system without hampering the communication flow. If you are confused about which SPF mechanism to choose, feel free to get in touch with experts at AutoSPF. We are here to enhance your domain security by simplifying soft fail and hard fail mechanisms for you.