You should fix up a version similar to skype v 2 or 5 or 6 that runs on all macs back to 10.6.8 or at least back to 10.9.5 that supports basic IM with audio notifications. To that, adding voice calls and video calls would be nice, but your current versions don't even handle IM notifications properly. For example skype 8.49 is the last version that runs on os x 10.9 and it doesn't work right. It only beeps on a new IM session and not on subsequent messages. This should be user-configurable and work right. As it is, I need to look for a new communication software.