appid to access mailbox

[merlin19]

hi i have created an interface where it pings a mailbox and searches a mail with xml case creation request file as an attachment from the mailbox which the client sends to create a case..now the client security team have told us that they wont give access to the shared mailbox due to some security reasons,,they have told us that they are gonna give us something called appid and password with which we can have access to multiple mailboxes .normal in my project when we used to use userid an password to access the mailbox i had added the required key in app config file..now with the appid and password i dont know how m i supposed to access the mailbox .KINDLY help me m new to the programming world