Invite frequent flyers to the shortest trip on earth – from doormat to computer. Tell the story in a mailing that consists of just one line, so it looks extremely simple. Make them log on to www.klm.com to switch to KLM's email service, and reward switchers with 500 free Bonus Miles.

The day after sending the mail, 10% of the target group had switched to email. A week later 20.5% had switched.