tech guide & how tos..
The SPF record is essentially a TXT entry in your domain's DNS records file that is controlled by you and viewable by all.
An SPF record entry in your domain's DNS file, enables recipient email servers to verify that a mail sent with sender as your email address has indeed been sent by you. Whenever a recipient mail server receives an email from your email address, it will check the SPF record in your domain's DNS file to verify the IP address(es) approved as your mail servers with the IP address from which it has actually received the email. If the IP address that it actually received the email from is not found in your SPF record, the recipient server will assume that the mail was sent by some imposter or spammer and hence would treat the email as spam and reject it.
The above method of IP verification ensures that no miscreant can act as an imposter and send out emails on your behalf. Thus it is essential to maintain an SPF record for your domain as it protects you.