IPGuru,
Normally I would agree with you but in this case there are issues with Avaya's design that would justify the need to restrict the user's options.
The Exchange Server integration requires you to configure the user to have Voicemail Email set to Forward. In theory the user then accesses and manages all their voicemails through Outlook. But by having to enable the feature using the Voicemail Email settings, all the user's other IP Office interfaces now provide them with access to their voicemail email settings which, if changed by mistake or curiosity, break their Exchange Server integration.
Nothing fatal but not the best user experience in the world to have to tell the user "re this option on your phone/prompt in your mailbox, don't use it".
On Avaya's part its a classic "did enough to get it working in the first build but never revisited it to smooth the rough edges".