Here's my setup: Multiple domain trees in a single forest (for the sake of explanation, lets call them domain1, domain2, and domain3). Single Exchange 2003 Server, which is a member of domain1. Clients use Outlook 2010. Each domain tree represents a different small company. There are people in the organization which need to be able to receive AND send email using email addresses from multiple domains. Research leads me to believe that this isn't possible using just email aliases, that sperate accounts are necessary. As a test, I setup an account for myself under domain2, and gave myself a mailbox. The mailbox was created, and I modified access and send as permissions. I can't attach the second account to my Outlook profile, it says "Name cannot be matched to a name in the address list." This appears to be an Offline Address List problem. I have verified that the AD email address matches the accounts primary email address. Our Offline Address List is configured to build based on the Default Global Address List. When I preview the Default Global Address List, the subject user shows up, but it does not show up in the Offline Address List. I have rebuilt the Offline Address List. I have turned off Cached Exchange mode. I have even increased the logging level of GAL building to maximum, and no errors are reported. I'm hoping this is just something stupid, that I'm missing. Thank you for reading, and thanks for any assistance.

Did you try to access the test mailbox using OWA by providing your credentials. Http://owa.domain.com/exchange/Testemailaddress Provide your credential and see if you can access the mailbox. I don't think this is OAB issue. http://social.technet.microsoft.com/Forums/en-US/outlook/thread/3ec522b6-10b3-4f4a-9ba8-5bdd37dbaf6c You can only add additional mailboxes to the profile's default\primary Exchange Account. -That's by design. But, you can exceed more than 3 Exchange accounts in an Outlook 2010 profile and each account will have its own set of folders. - Just like when you add an Additional Mailbox to your primary Exchange account. The difference between that and adding Additional Mailbox is that you cannot add more Exchange Accounts from within Outlook. You'd need to go through Control Panel | Mail | Show Profiles....Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Hasnain Shaikh| My blogs: http://messagingserversupport.com

Did you try to access the test mailbox using OWA by providing your credentials. Http://owa.domain.com/exchange/Testemailaddress Provide your credential and see if you can access the mailbox. I don't think this is OAB issue. http://social.technet.microsoft.com/Forums/en-US/outlook/thread/3ec522b6-10b3-4f4a-9ba8-5bdd37dbaf6c You can only add additional mailboxes to the profile's default\primary Exchange Account. -That's by design. But, you can exceed more than 3 Exchange accounts in an Outlook 2010 profile and each account will have its own set of folders. - Just like when you add an Additional Mailbox to your primary Exchange account. The difference between that and adding Additional Mailbox is that you cannot add more Exchange Accounts from within Outlook. You'd need to go through Control Panel | Mail | Show Profiles....Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Hasnain Shaikh| My blogs: http://messagingserversupport.com

Hasnain; Thank you for the response. I can access the account via OWA. The behavior I'm experiencing is exactly the same as when a user has "Hide from Exchange address lists" selected on their user account on the "Exchange Advanced" tab in AD UC (Users and Computers). Any other suggestions? Thank you, Dominic Hilsbos

Instead of Adding the test mailbox in your outlook profile. Whats the result if you try to configure the outlook profile for test mailbox. Did you try to add the test mailbox through Control Panel | Mail | Show Profiles.... Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Hasnain Shaikh| My blogs: http://messagingserversupport.com

Is it hosting environment? Fiona Liao TechNet Community Support

Result is exactely the same when I try to add the account to the profile. Also the same when creating a seperate profile for the account.

I'm sorry, I don't understand the question. We host all of our own software, however we provide technical support to several companies owned by the same person, so I guess you could say that it is a hosted environmnet.

Can you please post the error message you are getting. Also have you tried to configure profile for the test account on different workstation. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Hasnain Shaikh| My blogs: http://messagingserversupport.com

One of the central frustrations of this particular issue: there are no error messages (beyond the above noted "Name cannot be matched to a name in the address list." when trying to attach the account to Outlook). I have not tried to configure the account on a different computer, I will try that. I did try changing the account's username (I thought maybe there was a naming confilct, i.e. dhilsbos@domain1 and dhilsbos@domain2 wouldn't work together), no luck with that either.

I tried setting up the profile on a different computer, both in the "main" domain (domain1) and in the secondary domain (domain2), as well as trying to setup Outlook when logged on to the computer as the user account of the second Exchange mailbox. No luck on anything.

This seems to be silly answer but it has worked for me many time during PSS Support. Reset servers in following orders DC/GC Mailbox server CAS server Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Hasnain Shaikh| My blogs: http://messagingserversupport.com

for hosting related issue, please post the problem in: http://social.technet.microsoft.com/Forums/en-US/exchange2010hosters/threads, your understanding would be appreciated. Fiona Liao TechNet Community Support

I'm not using Exchange 2010, and I'm still unclear about what you mean by "hosting related issue." Could you please clarify what constitutes "hosting?" Dominic

Hosting means you host mailboxes for multiple organization within one exchange organization and create multiple address lists and Global address lists to make sure none of the companies can see any of the other organization users. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Hasnain Shaikh| My blogs: http://messagingserversupport.com

Ah, thank you for clarifying. We are doing the first part of that ("Hosting means you host mailboxes for multiple organization within one exchange organization"), but not the second part ("create multiple address lists and Global address lists to make sure none of the companies can see any of the other organization users"). We want all users to be able to see all email addresses. Regardless I'll go ahead and cross post this to the indicated forum. Cross-post: http://social.technet.microsoft.com/Forums/en-US/exchange2010hosters/thread/770ec9e0-187c-4860-8fb7-cfb81f48b0ce Dominic

This has not bee solved, and has not been replied to in the other forum. Moving this request to another forum is not an answer to the problem.