Sometimes I'll want to email someone but I don't know if their email address is valid. Likewise, they might have verbally told it to you, but you can't remember if it has a dot or a dash! Luckily, there's a handy way to find out using a mix of nslookup and telnet. I'll take you through a recent example where I wanted to email Ian Small, the CEO of Evernote, to thank him and the Evernote team for their wonderful Behind the Scenes videos.