If an institution is using custom API Keys on their forms, they will receive an email notification for the expiration of those keys. The message is unique depending on whether you are an Admin or a User.
CM Admins will receive a weekly email with a list of expiring/expired API tokens at their institution. The tokens that show up in this list are going to expire in 1 month or have been expired for less than 2 months. Anything that has been expired for longer than 2 months will not appear on the email list.
CM Users that have created their own API tokens will get an email at the following intervals prior to the expiration of each of their API tokens: 30 days, 14 days, 4 days, 1 day, and 0 days (the day of expiration).