SPF or Sender Policy Framework requires DNS records with the respective servers sending email listed. Most providers give you their SPF records, but none of them tell you how to implement two or more of them. If you don't configure these properly, your mail is far more likely to be marked as spam.
*This example does not include all of the servers necessary for MailChimp and Office 365 - It is purely for example purposes.
The record used is as follows:
v=spf1 include spf.protection.outlook.com include mcsv.net -all
For a more detailed explanation of various SPF Rules like -, +, ~, ? - That video should be coming soon.