In short, the ISP can trust the email is genuine and not fraudulently sent in your name, which is a common spammers’ trick. If you are following email marketing best practices, your good reputation and your verified identity should be enough to let the ISP know that your email is not spam and thus should be delivered. So by adding an SPF to include Benchmark Email, you will authorize Benchmark to send on your behalf, by verifying that we are doing the sending with the SPF Record.
Benchmark Email authenticates outgoing emails by using SPF and other authentication methods. You can find out more by reading our article on email authentication.
For someone without any SPF record, it should look like this without quotations "v=spf1 a mx include:bmsend.com ~all"
To check the validity of your SPF record, use the following tools:
For more information on some key concepts/points/topics, kindly refer the given links: