This library is for Ruby developers interested in accessing the SendGrid Web API v3. SendGrid is a cloud-based email platform handling thing from sending and receiving messages to managing email marketing campaigns.
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.
The line between what constitutes a software-as-a-service (SaaS) application and a platform-as-a-service (PaaS) environment has always been relatively thin. SaaS applications that expose an API to third-party developers can quickly transform into a development platform.