Google Gmail API

Google introduces new Gmail API which enables developers to use Gmail features into applications and make it easier for others to integrate and use as Plug-in.

According to Google:

The Gmail API gives you flexible, RESTful access to the user's inbox, with a natural interface to Threads, Messages, Labels, Drafts, and History.

The new API provides RESTful access to an inbox and supports CRUD operations on email threads, messages, labels etc.
The Gmail API can be used for a variety of applications including the cases where full inbox access is not required and the API can be much quicker compared to IMAP to search for a particular email.

The API provides fine-grained control to applications opposite to IMAP, where developers are required to obtain permission to the whole of an email inbox and therefore, will be restricted to:

• Read messages from Inbox
• Send messages
• Amend the labels affect to messages
• Search for specific messages

More Reading:

• Gmail API
• Gmail API Client Libraries