Google empowers Gmail with support for native add-ons
The new Gmail has support for native add-ons, which means they will now work across all platforms, including Android and iOS. Keep in mind that this is just the beginning, as Google announced that only three add-ons had been integrated with Gmail, all three aimed at enterprise users.
Salesforce add-on
Intuit QuickBooks will allow users to send invoices and confirm their status without having to leave the email app. With ProsperWorks, Gmail users can check the contact info of people on email threads against the info stored in their CRM.
Lastly, Salesforce add-on enables users the option to look up existing contacts, add new ones, and associate email threads with one or more existing opportunities in Salesforce, directly from Gmail.
Since these add-ons are contextual, they will appear in the email client when the need for them arises. It's also worth noting that Google invites developers who want to build new add-ons to sign up for the Developer Preview.
Things that are NOT allowed: