Exchange 2010 in AD environment - additional Accepted Domains

Question

I'm new to Exchange 2010 and I have some questions about impact of adding additional Accepted Domains.

We are set up with Exchange in Active Directory at domain.com and want to add others, domainhome.com and domainwork.com that are currently hosted outside.

Currently the ability to receive from domainhome.com and domainwork.com is valued higher than the ability to REPLY from those domains, but I should contemplate the option as long as I'm in there.

1. Is it sufficient to simply add Accepted Domains and transfer MX to our RoaringPenguin catcher - or is it necessary to configure Address Policies?
2. What is the impact of Accepted Domains on Active Directory - when adding user boss@domain.com do we automatically get boss@domainhome.com, or do we need to manually add that recipient? I see "automatically update e-mail addresses based on e-mail address policy" but am unclear whether everyone in domain.com will get additional addresses if there is no additional Address Policy.
3. In the event of 2 or more Address Policies, I understand one will be "default" for a given user based on sort order - if a user works for addresses in both domains - is there any clean way for them to reply from both? (Is it even possible?)

Answer 1

Is it sufficient to simply add Accepted Domains and transfer MX to our RoaringPenguin catcher - or is it necessary to configure Address Policies?

Adding a new accepted domain will allow Exchange to receive email on that domain. It still requires valid email addresses to be configured, which you can add either manually or with an address policy. Once you have your email addresses set up, point the MX record to your Exchange server and it should Just Work™. I'm not entirely sure what a "RoaringPenguin catcher" is, but if that is a service which takes your mail and forwards it to your Exchange server, then sure - point it there.

What is the impact of Accepted Domains on Active Directory - when adding user "boss@domain.com" do we automatically get "boss@domainhome.com", or do we need to manually add that recipient?

You will only get extra email addresses (such as domainhome.com, domain2.com) automatically from an email address policy. You can add specific email addresses to specific users, but that can easily become messy and unmanageable.

In the event of 2 or more Address Policies, I understand one will be "default" for a given user based on sort order - if a user works for addresses in both domains - is there any clean way for them to reply from both? (Is it even possible?)

As Evan says in his comment, this isn't really possible. Your primary SMTP address (i.e me@domain.com) will still be stamped on the outgoing email in the "From" field.

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Additionally, you'll need to think about migrating the emails in your existing domainhome.com provider to your Exchange server. Your provider may be able to help you with that, or if they're all in Outlook you can stuff them in a PST file and drag the contents of the PST file into Exchange.

You might also want to give the Email Address Policies articles on TechNet a read over so you understand how they work a little better.