Google, like many other email service providers, evaluates the authenticity of email senders by performing SPF record checks. Google does this to safeguard its users from phishing attacks and spammers.
To successfully send emails to Gmail accounts, you must implement SPF, DKIM, and DMARC to avoid getting rejected with a 5.7.26 error or landing in the spam folder.
Overview of SPF record check by Google
The way this process flows is as follows-
Receiving an Email
Gmail starts processing email as soon as it hits the Gmail account or any other Google Workspace service. So, when an authorized or unauthorized sender dispatches emails with your domain name, Gmail evaluates whether they should be placed in the inbox or spam folder or rejected.
By publishing a valid, well-updated, and error-free SPF record, you can ensure all the genuine sending sources are listed in it so that emails sent from them don’t get flagged as suspicious.
Valid and trusted sending sources refer to IP addresses (ipv4 and ipv6) and mail servers of people working in your company. It’s also advised to use the ‘include’ tag to add the sending sources of third-party vendors that communicate through emails on behalf of your business or organization.
Extract Sender Domain
Once an email hits the desired recipient’s Gmail account, Google extracts the domain name from the sender’s email address.
For example: example@autospf.com.
In this, autospf.com is the domain name. This is extracted to go to the respective domain’s DNS or domain name system.
SPF Lookup
Next, in the process of SPF record check Google, it performs a DNS lookup to retrieve the SPF record corresponding to the sender’s domain to verify if the particular sender is officially permitted to send messages on behalf of the company or not.
You can think of it as security guards allowing only those visitors whose names and secret codes have been enlisted in the guest chart given to them by the host or organizer. They won’t allow guests whose names are not mentioned in the list.
Check Source IP
Google checks if the IP address from which the email originated is listed in the SPF record as an authorized sender for the domain.
The result of SPF validation is positive if the IP address is listed and matches the SPF policy. Hence, the email is considered authentic. If the IP address is not listed or does not match the SPF policy, Google may mark the email as potentially suspicious or take other actions, such as placing it in the spam folder.
Summary
Email security is paramount to Google, and that’s why it extracts SPF records from the sending domain’s DNS to perform SPF authentication for email deliverability and spoofing prevention. The recipient’s mail server checks the DNS record and accordingly decides to place the message in the main inbox or spam folder or reject its entry.