Proxy addresses can be created either manually through the user interface or automatically by a proxy generation DLL. If your gateway serves a foreign system that does not already have proxy addresses in the Microsoft Exchange Server system, you will need to provide an Addr-Type object and an associated proxy generation DLL.
The proxy generation DLL implements a set of functions that the Microsoft Exchange Server calls to create proxy addresses. When a new address type is installed, the proxy generation DLL associated with the new foreign address type is called to generate a new, unique proxy address for each user. When a new user is added, the proxy generation DLLs for each known address type are called to create proxy addresses for the new user.
Because your proxy generation DLL must create a unique proxy address for each Microsoft Exchange Server recipient object, you should base your address generation algorithm on Microsoft Exchange Server address attributes that are already unique for each user. One unique attribute is the alias. Another possiblility is the pszCommonName member in the RECIPIENTINFO structure. You can combine unique attributes with other recipient information to form the proxy address.
Note The address type name is limited to eight characters. The proxy address itself is limited to 128 characters. Proxy addresses are limited to the 7-bit ASCII character set.
When you provide a proxy generation DLL, your gateway setup program must initiate the proxy address generation process. Microsoft Exchange Server automatically generates the addresses in the background while control is returned to the setup program. Gateway Setup Programs describes this process.