Just got this in my inbox from Ferris Research:
Dear Ferris Subscriber,
To ensure your continued interest in receiving email from our organization, we ask that you respond to this email.
Please confirm your subscription by clicking the link below or replying to this email.
We ask for your confirmation to protect you from receiving unwanted email. If you do not respond, you will NOT continue to receive email from Ferris Research.
Now that's a great way to run a clean email list.