want to use Spectrum e-mail for mailto handler

I tried using the Google AI to help with this and it gave me instructions to resolve the situation using developer tools, but was a dead end. I hit a roadblock trying to find a "uriTemplate" for another webmail service. The only one that had been on the mailto list was Gmail and I had removed it prior to starting this process, so there was no uriTemplate to be found. I tried calling Spectrum for help, but that was useless. Does anyone know another way to go about this?