I Am Not a FollowUpThen User:
FollowUpThen is an email reminder service that exists to make people more productive. If someone has figured out how to use our system to send you an unsolicited message, we apologize. This is completely against the terms of use of our service and our goals for the product.

You can permanently opt-out so we will never email you again.

If you wouldn’t mind, we would also appreciate it if you could forward the email to us at help+abuse@humans.fut.io

I Am a FollowUpThen User:
If you’re receiving reminders that you didn’t schedule, what is likely happening is called “email spoofing”. (A spammer sends someone an email but pretends to be someone else – i.e., you).  Fortunately, there are various methods of verifying a sender really his who they say they are. FollowUpThen can make use of these methods if you check the “Require Sender Validation” box on your settings page. This will cut the spammers at the knees. It just requires that your mail server supports at least one of the sender validation methods mentioned here. (Almost all large email providers do).  You can also, of course, permanently opt-out as above, but  this will prevent you from sending and receiving email reminders.