There is (was) a bug that would not allow you to send via email to an address that was in your address book if it was not the contact's "main" email address.
To explain, let's assume that you have an address book entry for John Doe, That contact has three email addresses (
), you can select any address in the contact entry, but the email will ALWAYS go to
because it's the first/main/primary email address in the contact entry in the address book.
Viigo says it's a BB OS bug, but I have only experienced it while using Viigo.