Route 53 and external mail server - SPF

SPF records can contain multiple include statements. If your domain already has an SPF record, you can add an include statement for Amazon SES by using the following format:

"v=spf1 include:_spf.google.com include:amazonses.com ~all"

You can use tools like https://mxtoolbox.com/SPFRecordGenerator.aspx to autogenerate the SPF recored, it will be helpful for you to understand the basics of the Sender Policy Framework and how to use it from these links:

• https://en.wikipedia.org/wiki/Sender_Policy_Framework
• https://support.dnsimple.com/articles/spf-record/

In addition to the SPF recored - https://senderscore.org/ or https://www.mail-tester.com/ are very useful tools to check you email score and provide you with additional recommendations for improvement.