Finding Duplicate E-mail (SMTP) Addresses in Exchange |

In this article, we will show you how you can find duplicate SMTP addresses in your Exchange Server organization. If your organization has non-unique SMTP addresses, Exchange returns the error when sending e-mail to those addresses:

Event ID: 9217
Event Source: MSExchangeTransport
More than one Active Directory object is configured with the recipient address [email protected] Messages to this recipient will be deferred until the configuration is corrected in Active Directory.

Multiple Active Directory objects are configured with recipient addresses.  Event ID: 9217

This e-mail message will not be delivered to the recipient.

When you create a new mailbox in Exchange Server and get a message that a user with that name already exists, you may encounter the following situation:

The proxy address SMTP:[email protected] is already being used by the proxy address or LegacyExchnageDN. Please choose another proxy address.

Proxy Address SMTP is already in use by Proxy Address or LegacyExchnageDN

To resolve this error, you need to find the Active Directory object that has the same SMTP address (alias) specified.

You can use the Active Directory Users and Computers console (aduc.msc) To find an AD object with a specific SMTP address:

  1. run console, go to Get , custom Search , advanced tab;
  2. Enter the following LDAP query: proxyaddresses=smtp:[email protected] (replace username and domain with your name);
  3. Click Get, Find out where proxy address is used in AD
  4. The console will display all objects that have a proxyAddress attribute that contains the email address you’re looking for. In this example, you can see that different AD objects (Users, Contacts, and Exchange Distribution Groups) can have the same proxy addresses;
  5. Change the value in the ProxyAddress attribute manually by using Active Directory Attribute Editor. Set up unique SMTP addresses for the items.

you can also use Get-ADObject Cmdlet from the Active Directory PowerShell module to find objects in AD:

Get-ADObject -Properties mail, proxyAddresses -Filter {proxyAddresses -eq "smtp:[email protected]"}

Because an SMTP address can be assigned not only to a user, contact, or distribution group, but also to an Exchange public folder, you sometimes need to use Exchange Server cmdlets to find objects that have the same SMTP address. :

Get-Recipient -resultsize unlimited | where {$_.EmailAddresses -like "*[email protected]*"}

Alternatively, you can export the full list of email addresses in your Exchange organization:

Get-recipient -resultsize unlimited | select Name -expand emailaddresses > C:\PS\Results\all_smtp_adresses.txt

User email address may include the following attributes: userPrincipalName, Match, proxyaddress, legacy exchange dneither msRTCSIP – primary user address, One of the tools for finding duplicate and invalid e-mail addresses is Microsoft IdFix (Directory Synchronization Error Remediation Tool). This allows you to test whether your on-premises Active Directory can be synchronized with Azure AD.

Finding Duplicate E-mail Addresses With Microsoft IdFix

You can use IdFix to quickly find all email objects that have non-unique SMTP addresses within your domain.

Once this is done, you only need to edit the SMTP Alias ​​or UserPrincipalName of a found object.

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