Personally I have been using https://www.appmaildev.com/en/dkim https://www.appmaildev.com/en/dkim most frequently as it allows direct input rather than sending

Personally I have been using https://www.appmaildev.com/en/dkim https://www.appmaildev.com/en/dkim most frequently as it allows direct input rather than sending mail which is often more convenient (ex: I am looking at a failing message). My only complaint is that for direct input it will say passed if any DKIM signature is valid, instead of reporting each. This often results in an AWS SES signature hiding the result of the one for the correct domain.