The “550 SPF check failed” message is a common error prompt that may be triggered by the absence of an SPF record in the sender’s DNS, the presence of an invalid one, or, third-party spam filters. The key takeaway from this type of error is that it is usually the sender’s fault, and not so much the receiver’s, and can be resolved with just a few quick steps.
SPF is an acronym for Sender Policy Framework, a protocol that forms the foundational element of email authentication and sender identity verification.
SPF records for domains reside in the DNS zone file of the sender and provide information about the IP addresses or domain names that are authorized to send emails on your organization’s behalf.
When you send an email from your domain, the email receiving server checks the domain’s SPF record to verify whether the domain name in the email’s return-path address is listed there. If no match is found, the email fails SPF authentication.
What is a “550 SPF Check Failed” Error?
The ” 550 SPF Check Failed” error is primarily caused by a misconfigured email server. This error can be fixed by modifying your DNS records or by adding a TXT record to your DNS settings for SPF.
It may occur when an email server attempts to verify the sender’s domain name using Sender Policy Framework, but it fails. If you’re receiving this type of error, it implies that your receiver’s server was unable to verify the email sender’s identity.
Probable Reasons Behind a “550 SPF Check Failed” Error
There are a few reasons that may lead to a “550 SPF Check Failed” error.
1. An Invalid SPF Record
The most common reason is that the sender’s SPF record is not valid. For SPF to function, a TXT type record is supposed to be added to your domain’s DNS zone file, but it is possible that it was not added or was missing some fields.
The way around this is by looking up your domain’s SPF record online to confirm the presence or absence of a valid record and eliminate this probability.
2. Microsoft’s Spam Filters
Microsoft’s anti-spam tool, Sophos, is an easy way to protect yourself from online hackers and malware infections.
Sophos is a free service that runs in the background on your computer and scans for corrupted code as well as spam emails before they reach your inbox. It also prevents malicious software from being downloaded onto your system.
However, if you relay your messages through Microsoft Office 365 Exchange online, your emails may fail SPF if you have Sophos deployed on your system. This will return the error message: “SMTP; 550 5.7.1 550 Message rejected because SPF check failed”.
3. Incomplete SPF record
Ideally, an SPF record should contain a full list of authorized servers permitted to send emails on behalf of a domain. However, more often than not, a domain owner misses out on specifying a legitimate third-party sending source. This can trigger the 550 error.
4. Messages relayed through one or more intermediaries
Multiple hops in between your email server and its ultimate destination (for example, if you’re sending through an external relay), means they won’t be listed in your domain’s SPF record and can be the probable cause for an error.
This is because during email forwarding when a message passes through an intermediary server, the email header information gets altered in transit where the return-path address now points to the intermediary’s domain. Your receiver’s server may not recognize this external relay as a legitimate sender, thereby returning “550 SPF Check Failed”
5. Spoofed Mail ‘From’ Address
Spoofed mail ‘From’ addresses are used to make it look like an email is coming from a legitimate source, but in reality, it is being sent by someone else. This can be done through any number of methods, including forging headers and messages or by directly using a legitimate domain for malicious purposes.
The problem with this is that messages using spoofed mail ‘From’ addresses do not pass SPF checks because the return-path domain doesn’t align with the mail ‘From’ (domain misalignment). The detected spoofing attack may trigger a similar error response and lead to SPF fail.
6. Multiple lookups
Lastly, another probable cause for the “550 SPF check failed” error is exceeding the RFC-specified DNS lookup limitation of 10. This can be the result of a faulty SPF record format returning a hard fail error that commonly appears with the subject line of “SPF Permerror”.
Troubleshooting 550 SPF Check Failed Error
If you are a victim to this error, note that the problem is usually instigated by the email sender and not the recipient.
You can troubleshoot it by following these steps:
1. Fix SPF Record Errors
An email sender can troubleshoot the 550 SPF Check Failed error by finding and fixing errors in their domain’s SPF record. These records are what allow for proper validation of your domain name. So even a slight spelling mistake or formatting issue can get in the way of the receiving server validating your domain.
The most common types of errors that can occur in an SPF record are:
- Extra spaces before or after the string
- Extra dashes
- Uppercase characters
- Additional commas and spaces
Some examples of a valid SPF record are as follows:
|v=spf1 include:spf-sender.example.com ~all|
|v=spf1 a mx ip4:126.96.36.199/11 include:example1.com include:example2.net ~all|
2. The MX Should Point to the Correct Server
When a sender sends an email, it is routed from their computer to a mail server (also known as an SMTP server). The mail server then accepts or rejects emails based on several factors such as their IP address and other information in their email header.
If an SMTP server receives an email with invalid MX records, it will return a 550 SPF Check Failed error message to indicate that something has gone wrong during routing.
To fix this issue, you need to ensure that your MX record points to the correct server. You can do this by editing the MX record of your domain in DNS Manager or cPanel.
3. Include your vendors’ IPs
To prevent missing out on including your vendors’ IPs, you can outsource your SPF management through a third party or keep a manual list of sending sources that are maintained and updated every time you implement an external tool or service for your emails.
Depending on these updates, you need to modify your domain’s records. There are specific guidelines set down by email service providers for aligning your sending sources. For example, if you use exchange online servers for message transmission, an Office 365 SPF record guide will outline these specifications for you to implement.
It is also important that your SPF record contains both your internal IP addresses as well as those of your forwarders.
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