They do, and I like how seamlessly mailto: links on websites work with web and local apps: your browser will give you a choice and either will work because email servers network with one another (obviously). Perhaps we could do this with linking to content across the Fediverse, with a custom URL scheme such as apub:@Blaze@reddthat.com. I explore this in my other comment at apub:post/20744080/11206632@reddthat.com.