Each letter in GetCourse has an integral block for letting a user unsubscribe.
If a user clicks on “Unsubscribe” link in a letter, subscription status remains the same, but subscription for a mailing category changes.
A user automatically subscribes for a mailing category at the moment of receiving of the first mailing. When user unsubscribes in a letter, he refuses receiving of mailings of a certain category. This action is recorded in a user card.
A user can change subscription status in his profile.
If when registering a user inserted wrong address (for example, @gmail.ru instead of @gmail.com), the first sent mailing will notice that, and subscription status for this user will be changed automatically.
Administrator can change wrong address in the user card. When changing of the address, a subscription of this user will be renewed.
You can track subscription statuses of users with the help of “Subscription status” condition.