I just want to make sure I understand: for micro.blogging, this @firstname.lastname@example.org` (if you have a custom domain name for your blog) works only if your domain is registered with micro.blog. Otherwise, you must use @email@example.com.
Nope-- my domain is registered elsewhere and works fine.
Same here, works fine for me too.
Just to add to that, registering a domain name with Micro.blog is offered as a convenience. There’s no technical difference between registering with Micro.blog or registering with another domain name provider.