SpamAssassin negative score for HEADER_FROM_DIFFERENT_DOMAINS

I solved this by completing the setup of 'MAIL FROM' in AWS SES. This set the mail from header in emails to be my domain name.

"HEADER_FROM_DIFFERENT_DOMAINS" and mail-tester.com now gives me a score of 10/10.

Note that for some email providers it took a few weeks before we were trusted and emails stopped going to spam.