XADM: NDR That Includes an "Ambiguous Recipient" Error Message Occurs When You Send a Message

In Exchange 2000, you may experience one of the following symptoms:

• When you try to send a message, you receive a non-delivery report (NDR) that includes an "ambiguous recipient" error message or a Simple Mail Transfer Protocol (SMTP) delivery status notification code 5.1.4.
• You receive the following message when you add a proxy address to a user account:
  This e-mail address already exists in this organization. ID no. c10312e7 Microsoft Active Directory - Exchange Extension.
• An event ID message similar to one of the the following messages is logged in the Application Event log when you add a proxy address to a user account:
  Event ID: 9514
  Event Type: Warning
  Event Source: MSExchangeIS
  Description:
  Two objects in the Directory have the same proxy
  /DC=COM/DC=[DomainName]/CN=[ContainerName1]/CN=[Object1] and
  /DC=COM/DC=[DomainName]/CN=[ContainerName2]/CN=[Object2]
  
  -or-
  
  Event Type: Error
  Event Source: MSExchangeIS
  Event Category: General
  Event ID:9549
  Description:
  An ambiguous SMTP proxy user1@domain.com was found on 0x2 mailboxes in the DS. The store cannot map this SMTP proxy to a unique Mailbox GUID.

This issue may occur if another account exists that has the same e-mail address.

To resolve this issue, locate the user account that has an ambiguous address or an address that already exists (to find the address, view the E-mail Addresses tab in the user account properties), and then change one or more of the accounts so that they do not have the same e-mail address.

To locate the user account that has an ambiguous address or an address that already exists, use either of the methods that are described in this section.

Method One: Use Exchange System Manager

1. Start Exchange System Manager.
2. Expand Recipients.
3. Right-click All Address Lists, point to New, and then click Address List.
4. Click the Filter Rules button, and then verify that it is set to Exchange Recipients (the default setting).
5. Click the Advanced tab, click Field, and then click User.
6. Click E-mail Address.
7. In the Condition box, click Starts with, and then type the first few letters of the address that you want to search for in the empty box to the right.
8. See the lower window for matches.

For additional information about how to locate user accounts that have specific addresses, click the article number below to view the article in the Microsoft Knowledge Base:

Method 2: Use Active Directory Users and Computers MMC

1. Start Active Directory Users and Computers Microsoft Management Console (MMC).
2. Right-click the root-level domain, and then click Find.
3. In the Find box, click Custom Search, click user in the Field box, and then click Proxy Addresses.
4. Enter a condition and a value to search for, for example, starts with and SMTP:user@.
5. Click Find Now.

NOTE: This method works for any proxy address type (SMTP, CCMail, GWISE, X400, MSMAIL, and other types).