You'd want to include your instance as part of your handle. I know, it's not as intuitive as a centralized service, but it is a requirement, especially when sharing the name elsewhere. So, your Lemmy account is [email protected]. Folks on lemmy.world don't need that, but folks on another instance (like me) would. I can get it from clicking your username, but there's no way to figure it out for a different platform from here.