I think I lean toward following Return Path's guidance on the topic, which boils down to this: Promotions tab placement generally shouldn't hurt read rate, customers still find your messages, and will still buy from you. Placement in the Promotions tab might even mean your mail is less likely to be reported as spam by Gmail users. And Promotions tab placement, Return Path rightly points out, is inbox placement. It's better than the spam folder.
Agency COSO Media attempts to address some raised concerns. Appealing directly to senders who have "noticed a recent drop in your open rate on your email marketing campaigns," COSO Media suggests that "the best way to get emails back into the primary tab is to have your subscribers put you there."
Email Service provider MailChimp similarly suggests that you "encourage your subscribers to take these actions: Add your From email address to their Google Contacts[, and] Move your emails to the Primary tab."
Collaborative email builder Chamaileon provides this checklist of considerations:
- Don’t sell
- Authenticate your domain with DKIM and SPF records
- Greet recipients by name
- Have no more than one link in the email
- Don’t include pictures
- Don’t use RSS campaigns
- Keep the email short
- Don’t use heavy HTML
- Lots of images in your email
- More than one or two links in your email
- If it’s “from” your brand, rather than you
- Lots of fancy HTML code in your email
- Links to your social media profiles in your signature
Maybe you can't follow every step suggested here. Maybe not every suggestion makes sense for every sender (I certainly see lots of "complex" HTML email messages in the Primary tab). But hopefully these suggestions give you some idea of things to try when troubleshooting this issue (or deciding that it's fine to leave as is). Got something to add? Share it in comments below.