All Marketing Cloud Emails seem to end up in Gmail's 'Promotions' Tab, even if the Send Classification is 'Transactional'. Anyone has ideas on how to make sure these emails end up in the 'Primary' tab? :)
Don't think there is a way of doing it. While I didn't find any related documents about marketing cloud, here are some posts from other email service providers. Below is one from Mailchimp:
Gmail delivers messages to tabbed inboxes based on complex and changing algorithms that consider subscriber engagement, content, and sender information. Messages from email service providers, like MailChimp, 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.
Article about this: