E-mail addresses in Exchange are supposed to be unique within the scope of an organization. If two users have the same e-mail address (not necessarily the same username, just the same e-mail address), e-mails to that person will bounce with a non-delivery report (NDR) that reads in part:
The recipient name is ambiguous.
MSEXCH:IMS:Microsoft:testdomain:SERVER1 0 (000C0595) Ambiguous Recipient
If you try to create a recipient that has an e-mail address already in use, the Exchange Server Administrator will report a similar error. If the message is sent via SMTP, an event ID 10000 will be logged with, again, a similarly worded error message.
There are several possible ways ambiguous e-mail addresses can be created. One is if the same address is created in two separate servers before replication is started or completed. For instance, if two separate organizations started inter-replicating without first determining if all their addresses were unique, this problem would appear.
To work around this issue, export a copy of the global address list from the server where the error is being logged. The GAL should be in .CSV format and should include mailboxes, distribution lists, custom recipients and hidden objects. The latter is especially important as ambiguous e-mails can often be attached to objects that are hidden deliberately, such as redirectors.
Import the .CSV file into a program such as Microsoft Excel, or another database or spreadsheet application. (If you have a very large GAL, use a database program, which will be more adept at handling a large number of rows.) Sort the entire list on the e-mail address field and the duplicates that exist will be paired up against each other.
It is also possible to find all duplicate addresses using a SQL query for programs that support it (such as Access or SQL Server).
SELECT email_address FROM csv_export_table GROUP BY email_address HAVING COUNT(*)>1
where email_address is the column containing the email addresses, and csv_export_table is the table containing the data.
Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.
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