Embattled BlackBerry said BBM is now available for download on Android and iOS devices. Customers, however, will not be able to use the app immediately unless they were one of the six million who signed up for BBM email notifications last month.

Following the botched BBM launch for Android/iOS in September, which saw at least one million Android users download an unreleased version of BBM from file-sharing sites that “caused issues” with the official client, BlackBerry is taking unusual precautions to manage BBM demand.

For those downloading the BBM app on Android or iOS (but haven’t already signed up by email) they’ll have to submit their email and join the activation queue.

BBM chief Andrew Bocking, in a blog, happily suggests the wait won’t be long. “We are focused on moving millions of customers through the line as fast as possible,” he says.

In a tweet on the official BBM Twitter feed, the company intimated it had seen five million downloads of BBM for iOS and Android in the first eight hours of availability. BlackBerry said: “Next 5 million in line – your turn!”

With BlackBerry in the midst of a strategic review which could see it broken up and/or sold, there have previously been reports that a spin-out of the BBM unit is a possibility.