You must configure the Messaging system to use the G.711 encoding format.
Note: The G.711 format provides the highest audio quality especially when voice networks use multiple encodings and decodings. Avaya requires that you use the G.711 encoding format in Messaging systems that support TTY devices.
The G.711 encoding format uses a higher encoding rate than GSM. The G.711 encoding format therefore produces larger files and requires more storage space for messages.
Messaging provides customers with adequate storage space for message playback and networking.
https://downloads.avaya.com/css/P8/documents/100172127

Avaya Breeze provides a virtualized and secure application platform where Java programmers can develop and dynamically deploy advanced collaboration capabilities that extend the power of Avaya Aura.
Customers, partners, and Avaya organizations can rapidly develop snap-ins and applications that are deployed on Avaya Breeze.

In Avaya Aura Presence Services, presence capabilities are not licensed separately on a standalone per-user basis. Instead, the user licenses for Presence Services are bundled as an entitlement within the broader Avaya Aura suite licensing (such as the Avaya Aura Communication Manager or Collaboration licenses). This means organizations that have the appropriate Avaya Aura suite licenses automatically receive the entitlement to use Presence Services for their licensed users, rather than needing to purchase a separate, independent license file or per-user add-on.

In an Avaya Aura survivability architecture, the Survivable CM remains in a "standby" or "LSP" mode as long as it can successfully communicate with the main, core Communication Manager.
The Heartbeat (Keep-Alive): The Survivable CM (LSP) and the main CM constantly exchange heartbeat signals to monitor network health.
Failure Detection: If the network link between the branch and the core is severed, or if the main CM becomes unreachable, the Survivable CM stops receiving these heartbeats.
Activation: Once the threshold for a "heartbeat failure" is reached (the LSP determines that the main CM is truly down), the LSP automatically activates itself. It then begins:
Accepting registration requests from IP phones that are configured to failover to it.
Taking its configured IP trunks "in-service" to allow the branch to continue placing and receiving calls over the public network or alternate PSTN gateways.