This client library written in Ruby allows developers build headers for the SendGrid SMTP API in Ruby. The SendGrid SMTP API allows developers to deliver custom handling instructions for email. SendGrid is an email application.
Google has released an updated Gmail API that functionally replaces the Email Settings API. The Gmail API includes a number of new endpoints that enable features previously unavailable through any Google API. Developers have access to filters, auto-replies, send-as aliases, and more.