An SPF (Sender Policy Framework) entry for your domain helps a server that should receive mail from your domain decide whether it is spam or not.
An SPF entry specifies which servers are allowed to send emails for your domain. In addition, the server that receives the mail is given advice on how to handle the mail.
This can, but does not have to, mean that the server that receives your mail tends not to classify the mail as spam. So you increase the chance that your mail will not end up in the spam folder, but directly in the recipient’s inbox.
We explain how to set up this SPF entry in the article What should an SPF entry look like?