Google had recently launched an 'Email Intervention' campaign to get users to switch from 'outdated' email to Gmail. What 'Email Intervention' does is more specifically getting exisiting Gmail users to invite their friends to Gmaill.
To help you a Email Intervention 'tookit' has been provided so you can create your own customised email to send to your contact using 'outdated' email.
One nice touch of the campaign are the viral videos in the style those retro tv ads, you know the calm, persuasive ones with the friendly presenter, a list of benefits and soothing background music?
Check out the campaign at the Gmail Email Intervention site.