DTMF digits coming at the beginning of a call from the PBX to MailCall can be viewed in one of two ways: "Inband" or caller control. If PhoneServer is configured to retrieve inband (Edit->Configuration->Answer Control) the digits coming in will be considered inband. Otherwise, they will be treated as user control digits. They can be the same digits coming in for both cases, they are just interpreted differently by MailCall.
Inband: The incoming string is treated as a failed called to that string. If other extensions are listed for this user the phone is transferred to the next extension. If no other extension is listed, a message is left for that user. All inband strings are stripped of '*' and '#' characters before being evaluated.
Caller Control: The incoming string is treated as caller trying to be transfer to extension. Call is transferred to the specified extension.
The PBX is forwarding a call intended for extension 1234 to MailCall due to No Answer. When MailCall picks up the ringing phone, the PBX sends 1234.
1 - MailCall is not set up to accept inband: MailCall will treat the 1234 as a caller trying to reach extension 1234. MailCall will then play the prompt "Please wait while your call is transferred" and transfer the call. If the customer is set up for blind transfers this will cause an infinite loop of calling 1234, forwarding to MailCall, transferring to 1234, forward to MailCall, etc.
2- MailCall is set up for inband: MailCall will treat the 1234 as a failed call and look up the mailbox 1234. If there is another extension listed the caller will be transferred to the next extension. If no next extension, MailCall will take a message for mailbox 1234.
1 - If the inband wait time is not long enough to retrieve the entire string from the PBX, the part it gets will be treated as inband the rest will be treated as caller control. For example, say in the above example the time expired between the 2 and the 3. The string "12" would be viewed as inband. The mailbox "12" would be looked up. If it was not found, MailCall will go to the main menu and then get the "34" string. This extension ("34") will then be looked up to attempt a transfer. If it doesn't exist, an "Invalid mailbox" message will be played. This means that the first message a caller hears could be "Invalid Message". Depending on how the inband was split up and the existence of other mailboxes, the caller could be transferred to the wrong extension.