We’re big fans of Rapportive here. Rapportive displays information about any email address you hover over when you’re in Gmail – tweets, links to social networking profiles, photographs, and more. It’s like the Gmail People Widget on steroids.
You can use Rapportive to quickly verify if an email address exists or not. Imagine you’re cold calling someone by guessing his email address – a glance over Rapportive on the sidebar will tell you if the email ID is valid or not – if Rapportive guesses the name of the person you’re emailing right away, and displays links to even one or two social profiles, you’re good to go.
Otherwise, if Rapportive just displays a question mark in the place of an avatar and doesn’t link to any social profiles, it’s safe to assume that the email address does not exist.
Got any interesting uses for Rapportive? Tell us in the comments.