SPF is Sender Policy Framework. This should be created from your DNS provider. If you are using our VPS for the Name Servers of your domain, then you can create the SPF Records of your domain from your Plesk control panel.
SPF fights return-path address forgery and makes it easier to identify spoofs by letting the domain owners identify sending mail servers in DNS. SMTP servers should verify the envelope sender address against this information, and can distinguish authentic messages from forgeries before any message data is transmitted.
While SPF can help prevent address spoofing, not all mail servers will reject a message if it fails the SPF check. You can learn more about SPF and create a custom SPF text by using the online wizard: http://www.openspf.org/wizard.html.
To create the SPF Record of your domain:
1. Login to Plesk control panel.
2. Select your domain and click on "DNS settings".
2. Click on "Add Record".
3. From the "Record type" field, select TXT.
4. Put the SPF Record (that you've generated from openspf.org) under "Enter TXT record".