MP3 isn't specifically on deck although technically we can support any codec that Windows does. If you check out the SetReocrdFormat.exe tool under commserver\utilities it'll show you all the codecs you can choose from currently active on the local system.
One thing to keep in mind, however, is that MP3 will chew up more CPU time for recording. We also support G729a which comes in around 1Kb/sec... MP3 doesn't do any better than that and it will almost certainly require more CPU resources to crunch it into shape, at least on the record end of things.
Just to be clear, however, we don't have MP3 codec investigation/testing on deck, but you're free to try whatever you'd like. You'll find folks out here that have tried various codecs to get messages playable on CE devices and the like, so fiddle away. If you find an installable MP3 codec that works OK, be sure to post back and let us know how it went.
Jeff Lindborg
Unity Product Architect/Answer Monkey
Cisco Systems
lindborg@cisco.com
http://www.AnswerMonkey.net (new page for Unity support tools and scripts)
