This example - So lets say we have 20 phones, but we actually want 50 mailbox's depending on the options the caller chooses. For Shoretel it's about 100 dollars per mailbox. But I was under the impression that with Avaya you just paid for the voicemail software and you could use it for as many mailbox's as you wanted.
If you are using DID's, route a DID to ring into a auto attendant box. In that box you can give users options to dial 0 thru 9, which could be another AA box, ring to a phone, take a message, company directory, or whatever you need. It is endless of how many steps you can make a caller go through. Are you planning to actually leave messages in 50 different mailboxs? If so, there is a issue with that. You do have to pay for a license for every mailbox that will take a message, because there has to be a user associated with it. What we have done, is given our callers the impression that they are leaving messages in different mailboxs, but they all end up in one or two boxes. Meaning, If you call our number and I give you the option to press one to pay your bill, 2 to ask billing questions, 3 to buy widget alpha, and 4 if you want to return widget alpha, they have the impression that they will be going to four different mailboxs, but I will send them all to the same one.
If you are not using DID, you can still make trunks ring to AA box and do the same thing.
Lets say you want it to ring to a phone first, and if it is not answered, you want it to go into all of these options. You can use the call handling modes to control this, or set it to happen all of the time. If you always want your calls to an extension to get options if there is no answer, set the standard call handling mode to forward the calls to the AA box. If you want to select when that will happen, like after hours, the user of the extension will just change their call handling mode when they leave. ( by the way, if you use outlook and PCM, you can set that schedule in Outlook and it will do it all for you).
Does that help at all? If you can give me more detail on what you are trying to do, I am more than willing to help.