Currently I am working with an environment that looks like this:
Smaller organization using Google Apps for e-mail, let's say this domain is @gapps-example.com
Larger organization using MS Exchange for e-mail, let's say this domain is @msexchange-example.com.
There is now a need to give users at the smaller organization AD accounts in the larger organization. Users should show up in the Exchange GAL with their primary e-mail address on record being their @gapps-example.com e-mail address. This alone would be easily doable using Exchange "Mail Users".
The hard part is that we also want to have a hidden / secondary "alias" e-mail address @msexchange-example.com that would auto-forward to their normal GApps @gapps-example.com e-mail address, for each user from the smaller organization.
This would be for odd cases where someone needs to verify their employment at the larger organization by getting a verification e-mail sent to them at an @msexchange-example.com e-mail address.
Does anyone have any advice on how to technically achieve something like this with Exchange?