I have a customer who is using Outlook 2010/Windows 7 against an Exchange 2003 server. The application is a on a laptop, remains out of the office and Outlook is configured to use RPC/HTTP.

I'm finding an oddity regarding authentication to the server.

Here's what's happening:

  1. The user can login to the Exchange 2003 server via Outlook 2010 if they authenticate with username/password.

  2. However, Outlook populates the username field within the authentication prompt with "username@domain.com" which the user cannot use to login to the Exchange server.

  3. This means that with each Outlook launch, they have to remove @domain.com from the username field and type their password. (The user does NOT want to save her credentials. Interestingly, if she DOES save her credentials, Outlook logs in automatically without incident.)

I think the easiest solution here is to somehow force the Exchange server (or RPC) to allow authentication via the email address. However, I don't know how to get that to work.

Another note: the Windows domain is not the same as the user's email address. Exchange handles my user's domain for mail delivery, but the actual Windows domain is different. I would be okay with the user logging into Exchange with user@windowsdomainname.com (It is a .COM, not .LOCAL or the like.)



1 Answer 1


It's actually more an Active Directory issue than an Exchange one.

Both DOMAIN\USERNAME and USERNAME@DOMAIN are functionally the same for Windows.

So unless the email domain is the same as the Windows domain, by default, USER@EMAILDOMAIN.COM will not work to log the user in.

That being said, you CAN do a work around by adding the email domain as a UPN suffix in Active Directory, then changing the user's UPN suffix to match email. That's generally only done in Hosted Exchange environments with separate GALs, mainly because the UPN suffix can then cause issues accessing domain resources, if the user is prompted to authenticate manually.

tl;dr - if it's only one user, I'd probably just have them authenticate as user@windowsdomain.com. If the user is important, there is a workaround, and I can walk you through those steps, but it can cause other issues.

  • Well, it doesn't seem like user@windowsdomain.com works either. I don't mind using that, however.
    – tcv
    Nov 21, 2011 at 20:54
  • Does authenticating as user@windowsdomain.com work in OWA? Nov 21, 2011 at 20:56
  • It does. I should note however that Forms Authentication is off. Perhaps that makes a difference.
    – tcv
    Nov 21, 2011 at 21:04
  • What kind of authentication is it using? NTLM? Nov 21, 2011 at 21:45
  • What do you mean by "it"? Outlook? OWA? How can I answer you?
    – tcv
    Nov 21, 2011 at 22:19

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