Implementing SPF involves adding a TXT record to your domain’s DNS settings. This record will list the IP addresses or hostnames of servers authorized to send emails on behalf of your domain. Here’s a basic example of an SPF record:
v=spf1 include:_spf.example.com ~all
In this example, "v=spf1" indicates the version of SPF being used, "include:_spf.example.com" specifies an external SPF record to include, and "~all" signifies a soft fail for non-authorized senders.