Unity doesn't limit the number of messages each user can have - this is a function of the Exchange mailbox limits - customers can apply levels to the entire site or on a per user basis if they wish. Here's a white paper that goes into some detail about how the storage limits work in Exchange 2000 that may be helpful:
You may also be interested in checking out the Message Store Monitor tool on www.CiscoUnityTools.com - it has the ability to set mailbox limits for groups of users easily and also has very detailed reporting capabilities on storage usage trends.
I don't know how to answer "what's the durection of each voice message"... not sure what you're asking here - it's as long as folks talk up to the maximum record time allowed - the max record time can be limited on a per subscriber and per call handler basis as you wish.
The storage needed for messages depends on the codec being used... the default G711 uLaw uses 8 Kb/sec - so a 1 minute message would be around 480 Kb. However you can also choose to use G729a which uses about 1 Kb/sec so a 1 minute message would be 60 Kb. Here's a white paper on the audio codecs in Unity that will shed some more light on that:
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The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
answer. Be sure to read the whole thing or e...
Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...