BlackBerry today began rolling out its BlackBerry Messenger (BBM) service to Android and iPhone devices.
The long-awaited cross platform offering, which was delayed after issues arose following the initial launch last month, is being rolled out in a phased manner.
BlackBerry is implementing a "line-up" system for access - meaning those who have already signed up for the service will be able to use it immediately, but those who haven't will need to wait.
BlackBerry said last week 6 million Android and iPhone customers had pre-registered for the launch.
BlackBerry's servers appear to be struggling under the load. At the time of writing users reported receiving a "temporary server error" on both Android and iOS applications.
BBM had initially been planned to launch last month, but was delayed after a leaked copy of an unreleased, older version of BBM for Android was distributed, impacting the system in "abnormal ways", BlackBerry said at the time.
It was forced to work on a fix to block the leaked version before the final version could be launched.