SPF Explained
Sender Policy Framework is an email authentication mechanism that allows domain owners to specify the IP address of mail servers that are authorized to send email on their behalf.
v=spf1 include:_spf.google.com include:salesforce.com ip4:1.2.3.0/24 ~all
Example SPF record allowing emails to be sent from Google Workspace, and Salesforce and the IP range 1.2.3.4/24.
Most SPF records consist of just a few
include: mechanisms that reference the SPF records of common email service providers (Google Workspace, Salesforce, etc.). Records end with either ~all (soft fail) or -all (fail) signifying that if they don't match any of the mechanisms, the email is not authenticated..SPF records are published as TXT records on your domain (e.g.
TXT yourdomain.com).