In the Fall of 2020, I had setup my .com domain's email server succesfully and after some modifications I seemed to have a working email address on my Handshake domain. It wasn't until February 2021 that I could verify this after running into another user (Sebastian Rasor) with a similar setup. As far as we know, it was the first independent mail transfer between two Handshake domains.
Afterwards, since many people have asked me how they could also setup their own custom Handshake email address—which is difficult for me to answer unless you already have a regular mail server running—I decided to setup a crude public email service where anyone could register a Handshake email address at the same domain name.
Thus, flip.flops was born. You can go and register your own @flip.flops email address so you can send/receive mail with other Handshake users! Currently, custom email domains are not yet implemented, though I eventually plan on making that happen. First I'd like to create a hosted nameserver service to easily allow others to set MX records for their HNS domains... and that requires setting up a whole ecosystem of UIs and backend software configuration beyond just the scope of email.
This is my personal Handshake TLD.
There are many like it, but this one is mine.