As you may know, Google recently launched a new interface for Gmail, which includes a tabbed categorization system. Among the tabs are: Primary, Social, Promotions and Updates.

It’s that “Promotions” tab that could pose a problem, and some companies who rely on email marketing are voicing their concerns, and going so far as to send their subscribers instructions to get their messages away from this tab. The question is how well will this work?

According to a report from The Wall Street Journal, companies like Delta, Gap, Groupon and LivingSocial have been instructing their subscribers to make the necessary adjustments to keep messages in their “Primary” inboxes. For some, this could be a hard sell.

Marketers are also worried other webmail providers will follow Google’s lead. The report shares the following quote from LivingSocial CMO Barry Judge:

“We think other email providers will be adopting this as well. We don’t know when and we don’t know who, but we think they will…We clearly just want users to see our emails.”

The report also shares the text retailer Kate Spade has sent to its subscribers, which says the “new inbox settings may have started filing away your Saturday.com emails into the depths of something called a ‘Promotions’ tab.”

The depths. That’s just it. This is a tab that users know they can go without looking at, as it it is just filled with people trying to sell them stuff. At least that’s what it’s supposed to be. We’ve seen non-marketing emails, like simple email newsletters filled with real content, appear in this tab as well. These are emails that users opted to subscribe to for said content, and now they’re likely getting ignored in the “depths” of this tab.

The situation is complicated even more by the fact that Google is putting its own ads in an email-like format in this tab – always at the top, of course. These aren’t actual emails. They just look like emails. Yes, they’re labeled as ads, but they look like marketing emails, and they compete for attention in the Promotions tab, where it’s already hard to get users’ attention.

There has been a little early research indicating that users who are “routinely engaged” with marketing email are reading a slightly higher percentage of their marketing email now. That’s according to Return Path, but it’s still early to have any truly reliable data on this.

One thing marketers might find solace in is that users who don’t like the tabbed interface (which includes pretty much everyone I’ve casually spoken to about it) can adjust the settings to make the interface more like the old style (without the tabs). It would be interesting to know how many are really reverting.