SPF (Sender Policy Framework) is used to authenticate your email. SPF is a DNS record that adds to your DNS. It contains your email server IP Address/Hostname of the sender's mail Domain.
Many email servers will bounce back the email or move the email to spam for the mail domain without having an SPF Record.
You can generate an SPF Record for your Domain from this link.
Steps to Add SPF Record in Plesk
Step 1: Log in to the Plesk Panel.
Step 2: Click on Hosting and DNS, then select DNS within this menu.
Step 3: Click on Add Record.
Step 4: Select TXT as the Record type from the Drop-Down and enter your TXT record, and click on the OK Button.
Step 5: Click on the Update button to apply the changes to the DNS zone.
Lastly, you will see the success message of adding the SPF record.
