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.
Our API directory now includes 199 email APIs. The newest is the Uptime Robot API. The most popular, in terms of mashups, is the SendGrid API. We list 10 SendGrid mashups. Below you'll find some more stats from the directory, including the entire list of email APIs.