What's the picture of half opened envelope with the number 21 beside it?

[WPCentral Question]

I have a icon at the bottom that looks like a half open envelope with the number 21 beside it. what is this? Seems my battery is really draining since this popped up.

 

[anon(5335899)]

You have 21 unread messages

 

[Kyle Stilkey]

I have a icon at the bottom that looks like a half open envelope with the number 21 beside it. what is this? Seems my battery is really draining since this popped up.

That would be your email.

 

[Dusan Randj]

At lockscreen? Maybe 21 new emails? Still, shouldn't drain battery.