Exchange 2007 SP1 Unified Messaging (UM) is currently the only officially supported voicemail solution for Office Communications Server 2007 and 2007 R2. Exchange UM offers three different codecs to store voicemails. A description can be found here.

When a company has many mobile users accessing emails (incl. Exchange UM voicemails) using their mobile (cell) phones, it makes sense to think about which voicemail codec to use as data plans for mobile devices are sometimes based on data volume. Also international data roaming can become costly so that the company can potentially reduce costs using smaller voicemail messages.

The three different codecs are:

• Windows Media Audio (WMA)
• Group System Mobile (GSM) 6.10
• G.711 Pulse Code Modulation (PCM) Linear

Before changing the voicemail codecs, an administrator needs to make sure that most of the currently used mobile phone devices are actually able to play these voicemail messages with that particular codec. One way to ensure this would be to send three emails to the mobile device with sample files of voicemail messages using the three different codecs.

In order to make this simple for you, you can download here samples of the same voicemail message recorded using the three different codecs. (It’s German and my voice, so don’t think there is something wrong with the file :-) )