This short post explains how to add and configure a Sender Policy Framework (SPF) record for a domain name, this allows servers to deliver mail when mail is not generally allowed away from the MX records you currently have setup.
THe SPF information should be defined in a standard TXT resource record when adding to your domain name.
Here is an example of what your DNS records should look like:
TXT:yourwebsite.com. IN TXT "description"
SPF:yourwebsite.com. IN TXT "v=spf1 mx include:yourwebsite.net -all"
This record is saying that mails sent from yourwebsite.net can send mail on behalf of yourwebsite.com
You would have received correct SPF records from Pebble to add to your current domain management area.