Whether your emails are delivered to your customers’ Promotions/Newsletters tab or their Inbox is typically determined by mail services such as Gmail. Given that you’re sending promotional emails, it’s only natural that they’ll be classified as Promotions/Newsletters by the Gmail algorithm.

Gmail is attempting to implement a categorization based on the following criteria:
- Email Content (whether the content you send appears to be marketing/promotional in nature rather than personal)
- Personalization (the level of personalization your email offers to each of the customers)
- User interaction (whether your customer personally marked your email to be categorized into the promotions tab)
If the content of your campaign is prepared as a single personalized email for each of your subscribers, the likelihood that your email will be delivered to the primary tab may increase.