Other Tools

DMARC Domain Checker
This tool allows you to check your SPF, DKIM and DMARC records all in the same place.
SPF, DKIM & DMARC Explained: How To Set Them Up And Combat Fake Emails
An introduction to what SPF, DKIM and DMARC is. This article also includes details on how it can be set up.
SPF, DKIM, DMARC: The 3 Pillars of Email Authentication
An short introduction to what SPF, DKIM and DMARC is.