Exchange Server 2010 SP1 Beta Hosting Deployment... Part #4 - Wait wait... are you saying mail contact actually works now? No way!

Hey folks, that's right, mail contact actually works properly now in Exchange Server 2010 SP1 Beta Hosting Deployment. I know many of you are saying, "Yeah, it is about time!"

So, it is true, each tenant can create their own list of contacts and not afraid of having any conflict with other tenant organization. Those who are in the HMC world today know just how difficult things can be to just simply have some contacts. If you have forgotten already, let me give you a quick refresh.

If you create a contact, ideally we should be able to set the proxyAddresses to the external address. This is all good in an enterprise environment but in HMC environment it isn't as simple. Because you are hosting multiple tenant organization, there is a potential that the contact of your tenant organization may also be hosted by the same hosters. Now, do you see the problem? It means in your environment, you will have a contact and a mailbox (user object) having the same proxyAddresses. Yes, those of you who has dealt with this before know that this will result in mail delivery problem because proxyAddresses need to be unique throughout the entire Exchange organization.

The way to workaround it is that, you use the attribute targetAddress and this will instruct Exchange to forward the mail for this contact to this address. Now, this is all good, it doesn't resolve the issue however that the proxyAddresses has to be unique. In order to maintain the uniqueness, some control panel provider has decided to issue it a number or a unique name with the domain of the tenant organization. Let me see how I can make it clearer. Say in your Hosted Organization, you have 2 companies, decides that he wants to create a contact in this tenant organization so that the rest of the mailbox users in his organization can use that contact. So, he created a contact like the following,

 Now, the above will create a problem because they have the same proxyAddresses. So, to work around it, it has to be like this,

 Now, you can see that the mail contact has the proxyAddresses of This way, there is no conflict and hence it will not interfere with the actual mailbox user. However, this create another problem which is the return address of that contact becomes instead of Meaning, if sends a mail to say, and cc the mail contact, then someone@hotmail.comwill see the address of CindyT as instead of the actual address of So, the workaround isn't that complete after all. One of the ways to go around that is perhaps writing a customized address rewrite agent for contacts at the transport layer. However, that means you have to manage an additional customized transport agent and that you need to deal with potential performance and scalability issue. In short, mail contact is sort of difficult because of the design of earlier version of Exchange. I hope I didn't confuse you folks now.

Exchange Server 2010 SP1 beta Hosting Deployment does not have this problem because there is proper transport level segregation. The transport is smart enough to recognize the context of an organization. In HMC, we don't really have a Transport level segregation and this has resulted in issue with this mail contact and also other issue such as OOF. I will blog about the transport later segregation in the next few blog entries. Then, you can probably see a have a much clearer picture and understanding on how everything fits in nicely.

To create a mail contact in Exchange Server 2010 SP1 beta,

Here is an example,

New-MailContact -Organization AlpineSkiHouse -Name "Cindy Lee" -ExternalEmailAddress

The above create a contact in the AlpineSkiHouse organization and the contact is pointing to a mailbox user another organization in the same environment. Obviously, needless to say, at the background, it will perform the necessary address list stamping and etc.

So, what do you think?

Previous Articles

Exchange Server 2010 SP1 Beta Hosting Deployment... Part #1 - The First Look

Exchange Server 2010 SP1 Beta Hosting Deployment... Part #2 - Creating New Organization

Exchange Server 2010 SP1 Beta Hosting Deployment... Part #3 - Creating New Mailbox

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Exchange Server 2010 SP1 Beta Hosting Deployment