An SPF record looks like this:
v=spf1 ip4:176.57.223.0/24 -all
where v — SPF version, always takes the value v=SPF1;
ip4 — IP address from which sending emails is allowed;
-all - mechanism for working with letters sent from other IP addresses.
This SPF record is simple and very strict. It allows sending emails only from the specified IP. All other messages should be blocked, as the "-all" mechanism is specified.
After the message is sent, the recipient's mail server checks which IP address the message came from. He checks it against the list that is written in the SPF.
If the address is on the list, then everything is in order. The letter goes into the inbox. If the IP address is not on the list, then the email may be blocked by the mail provider.
But if the SPF is not registered, there is a high probability that the letter will be delivered. And then scammers can easily write a message on your behalf and steal the personal data of subscribers.
Domain protection from spoofing. The main reason to set up SPF is to keep your domain secure.
Sometimes scammers send letters on behalf of another company or person, disguise themselves as a well-known brand, send messages “from the bank” about the transfer of funds, and ask to follow the link. They do this to steal user data, and money from a card, or to plant a virus program on a computer.
A scheme in which the sender of an email tries to impersonate someone else using someone else's logo and a similar email address is called a spoofing attack. To protect corporate mail and domain from blocking, and your subscribers from fraudsters, you need to configure SPF. Then the substitution of the sender will be less scary.
Delivery of letters to the inbox. Mail providers are loyal to senders who have set up email authentication, including SPF. Mailers are more likely to miss letters from such companies in their inbox.