I want to offer a multi-tenancy environment where multiple customers share a single Exchange organization. I use ABP to create dedicated GALs, ALs etc.

Now in a multi-tenancy environment it's common the case when multiple customer share a common contact (e.g. info@contoso.com); unfortunately I couldn't find any official guideline about how to manage such situations.

The problem is that in AD we can't have more than one contact with the same primary smtp address, but it happens that:

customer1 has this contact:

Name: Info_Contoso - PrimarySMTPAddress: info@contoso.com

and customer2 has this contact (different naming convention but same primary smtp address)

Name: InfoContoso Contoso - PrimarySMTPAddress:info@contoso.com

In our environment we basically assign a different primary smtp address for each customer and then we set a correct external email address, like this:

customer1:

Name: Info_Contoso - PrimarySMTPAddress: info_customer1@contoso.com - ExternalEmailAddress: info@contoso.com

customer2:

Name: InfoContoso - PrimarySMTPAddress: info_customer2@contoso.com - ExternalEmailAddress: info@contoso.com

These workaround works fine by a functional point of view but it's confusing customers using OWA as (in contact details) they see the (wrong) primary smtp address assigned to their own contact.

Do you have any suggestions to cope with this issue? I've noticed that this is not an issue in O365 (do they show a different field? unfortunately details template editor works for Outlook only, not OWA).

thank you

• Edited by climbing for fun 17 hours 42 minutes ago

I recommend that you post this in the Exchange for Hosters Forum:  http://social.technet.microsoft.com/Forums/en-US/exchange2010hosters/threads

Hi,

As what you mentioned in your posting, we cant create a contact in AD with the same primary SMTP address.

Why do you create the contact with the same naming convention in AD? And make it available for all tenant users. For example, customer1 in Tenant1 created a contact in AD:

New-MailContact -Name "Info_Contoso" -ExternalEmailAddress info@contoso.com -CustomAttribute1 Tenant1

When customer2 in Tenant2 creates contact with EMS:

New-MailContact -Name "InfoContoso Contoso" -ExternalEmailAddress info@contoso.com CustomAttribute2 Tenant2

There would be an error says The proxy address SMTP:info@contoso.com is already being used by Domain.com/Users/Info_Contoso.

Then the customer2 can set the contact for Tenant2:

Set-MailContact -Identity Info_Contoso -CustomAttribute2 Tenant2

We can use the CustomAttribute1 and CustomAttribute2 to filter Mail Contacts in AD to create the address list in GAL with ABP for different Tenants.

This is my personal suggestion as a workaround. If you want to find another solution for your requirement, please ask a question in Exchange for Hosters forum for more help.

Regards,