There are limits on the number of channels that the voicemail server can use for outgoing calls it can make. The limits are separate for each type of outgoing call type. When a limit is reached, further calls of that type are delayed until one of the existing calls is completed. These limitations are not controlled by Voicemail Channel Reservation settings in the IP Office system configuration. They depend on the type of IP Office system controlling the voicemail server.
Outcalling can use up to 5 (IP500 V2) or 12 (Linux-based) channels at any time.
Conference center invitation calls can use up to 5 (IP500 V2) or 12 (Linux-based) channels at any time.
Callback calls can use up to 2 (IP500 V2) or 5 (Linux-based) channels at any time.
Alarm calls can use up to 2 (IP500 V2) or 5 (Linux-based) channels at any time.