Message Waiting Indicator (MWI) issue between Avaya Aura Communication Manager and Exchange Server 2010 Unified Messaging Integration

Problem

You currently have the following telephony solution in your organization:

PBX: Avaya Aura Communication Manager Version R016x.02.0.823.0
Voicemail: Exchange Server 2010 Unified Messaging

The Avaya Aura Communication Manager PBX is fully integrated with Exchange Server 2010 Unified Messaging with MWI (Message Waiting Indicator) functioning as expected but you recently noticed that the MWI is either permanently off or lit up regardless of whether users have voicemails:

Solution

While there can be many reasons that can cause this problem, I recently found that this can happen if the Exchange 2010 Mailbox Server’s Microsoft Exchange Mailbox Assistants (MSExchangeMailboxAssistants.exe) service is stopped:

Basically what happens when this service is stopped is the following:

MWI not already lit up on the phone – New voicemails received will not light up the MWI light

MWI already lit up on the phone – MWI light will continue to be lit even after all voicemails have been listed to or deleted

This can be fixed by simply restarting the service.