Two Domains, Two Users - joe @ domain1.com & joe @ domain2.com - How?
It is well known that Exchange can handle more than one domain. This is achieved by simply adding the extra domain to Accepted Domains and then Email Address Policy.
However where the problems come in is having two users (in this example both called Joe) who want joe@their domain.
If their username (on the WINDOWS domain) is joe, then the Email Address Policy will automatically stamp joe@domain1 and joe@domain2 to the account.
First thing to worry about is Active Directory account creation.
Don't have either account with the user name of joe. Make them joe.smith and joe.jones as the username. If this isn't possible then ensure that the second one is called something different when setting it up.
Automatic Email Addresses
If Email Address Policy hasn't already, configure joe.smith@ and joe.jones@ as their email addresses on both domains. This will ensure that they have unique addresses. This is just a interim step.
The key point is that if you create an account with "joe" as the username then the Email Address Policy will apply joe@ to all domains on the first account. If that has already happened, then you need to follow the process below so that you manually control the email address and can remove the clash. However, remember to allow time for the domain to replicate that information before trying to apply the email address removed to another account.
Taking Control of Email Addresses
For this process to work you need to control of the email addresses.
- In each user, go in to the Properties, then the "Email Addresses" tab. On that tab is a selection for "Automatically update email address based on email address policy". This should be cleared so that it isn't enabled.
- Hit apply for that setting to take effect, but don't close that tab.
- Now change the email address to be your preferred address - including making it the reply to address as required.
- Repeat for the other user.
The end result is two separate accounts, both with joe@ as their email address.
Avoiding this Problem to Begin With
There are a number of ways of avoiding this problem.
- Don't use single names as email addresses.
While this can be "cute" it does indicate that you are a small company. Most companies of any size will have at least one name clash.
Instead use something like firstname.lastname which will avoid most clashes.
Obviously there are exceptions to that - it is not uncommon for the owner to have a first name only email address, and the IT staff will also give themselves single name email address.
- Use a different naming convention for usernames.
If you are hosting multiple companies then create usernames that make them unique to that company.
One example would be something along the lines of joe@trucks, joe@cars, joe@vans etc
You could even make the username the email address!
Two Domains One User - How to allow a user to have two email addresses on the same Exchange server