Fashion resale app Poshmark has amassed a devoted audience of female millennial users who spend an average of 25 minutes a day shopping, selling, bargaining and otherwise engaging in the mobile app.

Across social channels, you can see the expected posts praising the selection of items for sale in the app and shared excitement about the ability to make money selling closet overflow, but the majority of user posts are praising a very unexpected Poshmark feature: their twice-daily  push notifications.

Push notifications are most commonly used by media companies, who blast out breaking news and sports scores to their mobile app users, and some e-commerce apps use notifications to deliver time-sensitive pricing announcements and shipping confirmations, in hopes of driving up mobile sales.

But Poshmark uses that precious lock-screen real estate in an entirely different way: They consistently deliver an inspiring, motivational, playful or relatable saying to their users. No branding. No product mentions. No links.

"Relationship status? Who cares. You're fabulous!"

"When you nod your head yes, but your wallet says no...What do you mean?"

"Our favorite type of men? Ramen."

"The push is not about us, it's about them," says Kate Franco, Senior Director of Merchandising and Product Marketing at Poshmark. "We aim for each push notification to feel like a text from a friend who deeply understands them."

If the  volume and sentiment of praise on Twitter is any indication, it's working. @Poshmarkapp has more than 84K followers, and the account frequently retweets some of the  35-50 daily user tweets that pair notification screenshots with emojis and profuse praise.

“Push notifications work well with my generation because they are quick, short and mobile,” says Dan Schawbel, Millennial Expert and bestselling author of Promote Yourself.  “Millennials want to not only consume short-form content, but share in the experience with their friends online."

“When we began experimenting with creative push notifications in 2014, we instantly saw a 35% increase in CTR and we knew we were on to something,” Franco says. In monitoring their social channels, they noticed the uptick in users sharing screenshots, and they use that data to inform and optimize future notification content. They now see users opening the app an average of 7-to-8 times per day.

“The key thing going on here is novelty,” says Jeremy Goldman, CEO and Founder of digital consultancy Firebrand Group, and author of the upcoming book Getting to Like. “The Poshmark approach is novel and unexpected, which is why it works.”

“These push notifications have become a cornerstone of the Poshmark voice,” Franco says. “We are able to differentiate ourselves in the sea of push notifications that users receive every day by using the voice that came most naturally to us: Poshmark as your BFF.”