By serious email address, I assume you mean like business emails such as
name.surname@companyname.com, right? This means you'd need an e-mail hosting service instead of a webmail provider (gmail, yahoo, hotmail, etc). Sure you get a custom domain name, but you'll have to pay money. Looking at LuxSci, an individual account starts at $11.34 a month for domain name, 2 gigs of space, and security/spam protection.