Multiple email addresses to 1 AD account

I have 3 email addresses app1@test.com, app2@test.com,app3@test.com. I would like to authenticate them against just 1 AD account like application_auth@testad.com

Or 1 email address to 1 AD account with a different name

I have an email acocunt joejohn@test.com. His AD account is jdoe@testad.com. Without phyiscally changing the email address or the account name can you create or add to the email/AD mapping filter to match these up?

Basic Overview Question:

How does Zimbra (what fields are used) go about looking up an account in Active Directory?

thanks

Doug