Instagram is getting on board with email. The popular social network started sending out "highlights" emails to some of its users this month. Like Twitter's similar "best of" emails, the messages serve up a sort of recap of what's been going on in your social network. More importantly for Instagram, the emails serve as a way to keep the photo sharing service at the front of users' minds. An email here or there can help occasional users interact with the service without committing to opening the app every day or week. It also, Instagram hopes, lets users know just how much fun they're missing out on by not using the app frequently. An Instagram spokesperson has confirmed to TechCrunch that this is the first time that it has used email to promote the service. Keep an eye out for that unsubscribe button in your inbox soon.