Instagram is in many ways an anomaly in the world of social media.

A frenetically popular platform that remains largely ad-free, still allows brands to connect to fans without paying, and doesn't really market to its users. Being owned by Facebook doesn't hurt,

However Instagram might be edging more towards the mainstream with its new 'Highlights' email feature.

High mark?

Instagram has started sending a Highlights email to selected users, which displays the top posts from those they're following.

Rival platforms like Twitter have long sent similar emails, however this marks the first time Instagram has ever sent users any form of promotional content.

Interestingly, at the time of writing there appears no way to control or unsubscribe from Highlights.

Turning point

Highlights might help lure back users who have strayed from the app in recent times, and encourage others re-engage with content from their favourite accounts.

It may also annoy users who aren't given the option to opt out.

We'll have to wait until Instagram release their next round of stats to see how engagement levels react.

We're predicting they'll continue to rise.