Supporting multiple email domains in Exchange 2003

If you have an Exchange 2003 Server or an SBS 2003 machine, you may need to allow it to receive email for multiple email domains. There is a basic procedure you should follow to enable you to do this.

The following article assumes the following:


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Receiving Email
Receiving mail for the new domain is relatively simple. Ensure the external DNS records are configured so the MX record for domain2.com points to your server.
Go to Exchange System Manager, Recipients, Recipient Policies.
Right Click on the Default Policy and select Properties
go to email addresses and click on new, SMTP address

enter the new address in the format.
@domain2.com

Select OK.

After a short while, all your users will now have new email addresses configured, which you can verify in Active Directory Users and Computers. (You can speed this process up but it will happen)

You can individually change the default for each user, or set the default for all users in the recipient policy.
You can also create another recipient policy and have this applied only to selected users or groups.

Sending Email
By default, sending email will always appear to be from the default email address - even if replying to one that was originally delivered addressed to another address.
If you have users who are on either domain1 or domain2 this isn't a problem.
However, sometimes you may have staff that wish to choose which domain to send from.
Such as when a business is functioning under 2 trading names, or when you want to send an email from either user1@domain1.com or sales@domain1.com

Exchange/Outlook doesn't directly support this option. The FROM field in Outlook allows you to send from another USER (subject to permissions) not from an email alias.

So to give the user a choice:

Create a second account using pop/smtp (slightly different location depending on which version of outlook so I wont give specific step by steps)
Set the email address as the one you want to be able to use.
Set the incoming and outgoing server as your exchange servers local server name.
Set the username and password as your domain username/password.

the additional trick required, is then in outlook.
tools, send/receive, send/receive settings, define send/receive groups
all accounts-edit
select your new pop/smtp account on the left.
untick 'receive mail items'

this will stop outlook from Popping your email - only to try and put it back into the same mailbox.

You will now be able to send as either account.
when you create a new mail message - you will have  a new button on the toolbar "accounts" that will let you choose which account to send via.
In addition, you can create other signatures that become the default for each account - so you completely look like the other company.

Drawbacks of the choice of sender.
this doesnt work with outlook web or outlook mobile access - these will only use your default mail account.
people (eg secretaries) that send on your behalf will only use the default.
Some manual work required at the workstation so not as easy to configure with group policy.

An alternative is to create additional users for the second domain and then 'primary/real' user access to that mailbox and send on behalf permissions.
This does keep the emails sent to that domain completely seperate, but does make for more effort for the user to view additional mailboxes. It also means additional admin work to create second active directory users, passwords etc for each user.