Some references to it can be read from: https://docs.aws.amazon.com/pinpoint/latest/userguide/channels-email-deliverability-dashboard-pipt.html
Also, you can utilize https://mxtoolbox.com/MXLookup.aspx or other tool such as https://www.dmarcanalyzer.com/spf/checker/
Some tips are putting this on your DNS https://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-authentication-spf.html
Best,
Doddi