BlackBerry BBM is heading to Android and iOS devices.

BlackBerry said Monday that its popular messaging service BBM is heading to Android and iOS devices. BBM fans who signed up on the official site will be able to use the application immediately. BBM fans who signed up on the official site will be able to use the application immediately. But those who haven't can download the app to "hold your spot in line," and will get an e-mail when they can start using the service.

BlackBerry said 6 million people signed up for information on BBM.com.

"If you didn't sign up in advance, don't worry -- we are focused on moving millions of customers through the line as fast as possible," the blog said.

BBM was supposed to launch last month, but was pulled after a leaked copy was distributed and performed terribly in the wild. BlackBerry said the unintended launch caused issues that the company needed to resolve.

The fervent demand for the app is a counterpoint to the common thinking that BlackBerry isn't long for this world. While sales of its newer BlackBerry 10 devices are in retreat and the company has whittled its focus down to the big businesses and governments, BBM persists as a popular messaging platform.

BBM continues to be a popular platform around the world, particularly in emerging markets where cheap, older BlackBerrys are still in demand.

Still, the delayed service for many casual users interested in BBM may turn off some users who had abandoned BlackBerry to go to Apple or Android, but were interested in reconnecting with BBM friends.

A version of this article originally appeared on CNET under the headline "BlackBerry BBM finally hits iOS, Android, but there's a wait list."