implicit log on for OWA

Hello all

running exchange 2003 sp1 on windows 2003 sp1. I host two domains on my server for two companies. Both companies share a common GAL, and both companies can log into OWA or outlook via there primary email address. I.E bob@comapn@.com and bill@companyB.com.

It seems after applying SP1 for exchange user no longer have to log into OWA as user@primaryemailaddress.com they can now log in as ther username.

This is cool, but why is it working like this after applying SP1? also all users log into outlook via RPC over HTTPS. When logging in via outlook the user still must log in via primaryemailaddress.com. Is there a way to change this so the users logging in via outlook can log in as username?

Many thanks