OWA 2013 multi-tenant shared contact

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)

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:

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