Guerilla Mail is a simple idea with one purpose: to avoid spam. The idea is dead simple: go to the website, it gives you a random e-mail address that's good for one hour, and links to nothing else. Register for sites or whatever with it, and then never worry about it again. Although the Web Service is convenient, sometimes it's not everything you need. For those cases, one might want to look into using the Guerilla Mail API.
Here's how Guerrilla Mail describes its service:
Guerrilla Mail gives you a disposable email address which lasts for 60 minutes. There is no need to register, simply visit Guerrilla Mail and a random address will be set. You can also choose your own address.
You can give your email address to whoever you do not trust. You can view the email on Guerrilla Mail, click on any confirmation link, then delete it. Any future spam sent to the disposable email will be zapped by Guerrilla Mail, never reaching your mail box, keeping your mail box safe and clean.
The API is designed to be used exclusively through AJAX and JSON, with typical HTML calls. No API Key is needed, although it does require the transmission of the current IP of the user via plaintext, as well as the user agent string for the user's web browser. It allows the same functionality as the website, and some additional tricks such as setting the e-mail address to one of the user's choice. This API might allow, as an example, a developer to make a truly paranoid web browser, integrating Guerilla Mail into it for website registering purposes.