Right but if you're not hosting Web content then you wouldn't want it linkified in a Web context. If you're using it for something else, e.g. SMTP, then you'd represent the domain name differently as [email protected]

Why wouldn't someone follow the standard of prefixing it with an appropriate subdomain? E.g., `smtp` or `imap` if it's something they're going to be discussing publicly?

Furthermore, why not use port numbers as a suffix? That's how we can have umpteen services across different protocols on a single domain.