You can cancel your CloudMailin subscription at any time from your user page. There are two options, depending on how much you want to remove:
The Delete All Addresses button on your user page deletes all of your addresses and cancels any paid subscriptions. You will no longer be billed, but you can continue to log in and create new addresses later if you need to.
The Delete User button removes your user, your account and all associated resources. You will not be able to log in again afterwards.
Both actions take effect immediately and cannot be undone. Neither deletes resources in an account owned by someone else, such as a team account you are a member of.
If you signed up through a provider such as the Heroku add-on, that provider handles your billing, so the subscription must be cancelled there — remove the add-on from your application and the CloudMailin account will be cancelled automatically.
If you want to reduce your bill rather than leave, you can switch to a smaller plan — including the free plan — from the plans page. See the refund policy for how refunds are handled, or contact us if you have any questions.