An SPF (Sender Policy Framework) check failure means that the email server receiving the message is unable to verify that the sender of the email is authorized to use the domain specified in the SPF record.
To resolve this issue, you need to add the IP address of the server sending the email to the SPF record of your domain.
Here's how you can do this:
Log in to your domain name registrar's account where you manage your domain name.
Locate the section where you manage the DNS records for your domain name.
Add a new TXT record to your DNS configuration that includes the following information: "v=spf1 include:example.net ip4:<IP Address> -all" (Replace <IP Address> with the actual IP address of the server sending the email.)
Save the changes to your DNS configuration.
Wait for the changes to propagate, which can take up to 48 hours.
By adding the IP address of the server sending the email to the SPF record of your domain, you will resolve the SPF check failure issue and ensure that emails from your domain are not marked as spam.