spf

You might already know, that you can use either a Sender Authentication Package or Private Domain to brand your emails, so the sender email address reflects your brand. In almost all cases, this sender domain is a subdomain to your business domain. Assuming your website is based on example.com, the sender domain can be mail.example.com

Email authentication helps to ensure that an email message was sent by the domain it claims to be sent from, and that the message has not been modified in transit. Authentication is the effort to equip messages with enough verifiable information so that recipients (ISPs and end consumers) can recognize the nature of each message