as there may never be a platform such as Kdmarc to double check issues with my email domains for deliverability issues and spam-o-meter

Platform might be a bit complicated for regular users if you are not familiar with technical terms such as DMARC or DKIM or SPF... If you haven't configured a domain email from scratch, you'd need to learn it a bit. Kdmarc, makes it a tad easier to configure DMARC with some additional benefits.

Make sure to at least grab one before they disappear from the store in less than 8 hours!

Cheers,
Mike
MySoftwareAdviser