There are certain online services to which you may not want to subscribe permanently due to various reasons. You may not need to use it once again or the service is known to send promotional mails frequently. Disposable mails are a handy option in such cases. They are temporary email addresses which last for a short duration but long enough to receive verification mails and complete a subscription to any website. You can then use the credentials to login and finish your business.
Search disposable mail in Google to find such services. The one I frequently use is MintEmail.