Outlook 2007 with Exchange 2010 supporting multiple domains

Hello,

I have a design question regarding Exchange 2010 and Outlook 2007.

Currently, we have a SMTP/POP3 server that accepts several domains, let say: companyA.com and companyB.com, where both names are aliases, meaning e-mail sent to an address@companyA.com can be retrieved with address@companyB.com and vice versa. Most of our users send messages from their Outlook using only one address. But some users work for both companies and need to be able to send messages from both addresses.

Right now, this is implemented by having two POP3 accounts in Outlook. The user needs to select the correct account only before sending the message. The advantage of this is that the user has a personalized signature for each account.

We are about to move to Exchange 2010 for our mail services and I need to implement something similar. As Outlook 2007 allows only one connection to Exchange 2010 I have two options in mind:

First option: Set the primary account, the one that the user will use more often (for example in companyA.com) as Exchange account and the second one (for example in companyB.com) as POP3 account. The advantage of this approach will be that the Outlook users will still be able to attach their signatures to the account and they will continue to function in the same way. The disadvantages are: we need to open POP3 access to the CAS and this does not work in OWA

Second option: Set only one account as Exchange account and train the users to use the From: field in Outlook. Advantages: no need of POP3 access and it’s the same in OWA. Disadvantage: the user will need to pay attention to the signature and change it as well.

I think I am going to choose the first approach since it will be less stressful for the users.

My question: Is there another way to do that?

Thanks