How do you make your MailChimp email go into someone's primary Gmail inbox instead of the Promotions inbox?
Short answer: You can't.
The individual Gmail user can so choose. YOU cannot. (Thank you Google!)
Gmail is very sophisticated. Mailchimp (and other mass marketing email senders) are *correctly* identified by the sending domain - which makes them Promotions. So they go to the Promotions tab (it's not an inbox) - by default.
You (the sender) cannot change which tab your mailchimp emails appear under. To do that, you would have to create/use a different domain - not mailchimp.
And not any other known mass mail sender, either.
If the recipient wants your emails to appear somewhere else, they can right-click on the email, and move it to the desired tab. Gmail will then remember this preference for future emails from that sender.
Source - quora
Gmail delivers messages to tabbed inboxes based on complex and changing algorithms that consider subscriber engagement, content, and sender information. Marketing and bulk emails often have a higher chance of being delivered to the Promotions tab.
Unfortunately, Mailchimp has no control over the placement of emails in Gmail, and there is no proven way to "beat" Gmail's algorithms. Only a subscriber can move your emails from the Promotions tab to the Primary tab.
In this article, you'll learn about Gmail tabs, and what subscribers can do to ensure your campaigns are delivered to their Primary tab.
Benefits of the Promotions tab
Gmail's Promotions tab contains marketing emails and promotional offers. When Gmail introduced inbox tabs, many marketers worried that subscribers would overlook mail in the Promotions tab.
Fortunately, studies show that people use the Promotions tab. According to ReturnPath's study of three million Gmail users, the tabs improved deliverability, increased open rates, and decreased spam complaints. Plus, Gmail's inbox organization doesn't affect all your Gmail subscribers. Inbox tabs are optional for Gmail users, and many people disable them