Hi,
The problem is caused by an incomplete SPF record. You are using Amazon SES (possible by using the Acymailing Sending Service). You should allow the Amazon servers as sending server by adding it to your SPF record.
Change v=spf1 mx a -all
into this: v=spf1 mx a include:amazonses.com -all
After making the change wait for the dns record to fully propagate and then run the mail tester again.