Resolved mailbox migration error: “Target Mailbox Doesn’t Have an SMTP Proxy Matching”

Advancements in cloud computing are compelling numerous enterprises to migrate their email communication process to online. The features in a cloud-based environment have become more reliable than the offline versions.

One of the robust online email cloud services is Exchange Online, offered by Microsoft, which is an online adaptation of their offline Exchange On-premises Server. The Exchange Server is used for managing email communication within an enterprise. Most of the Fortune 500 companies rely on Exchange Server for their day-to-day emailing.

A hybrid Exchange environment accommodates both the Exchange on-premises and Exchange Online; occasionally, users move their mailboxes from one to another. But sometimes the process is halted by an error message stating:

“Target Mailbox Doesn’t Have an SMTP Proxy Matching”

The occurrence of such an error in the middle of mailbox migration can raise concerns among the users regarding their data. Here, we will discuss how to fix mailbox migration error “Target Mailbox Doesn’t Have an SMTP Proxy Matching”.

“Target Mailbox Doesn’t Have an SMTP Proxy Matching” error: Core Reasons

Before initiating the solution, let us first understand why we are experiencing the error “Target Mailbox Doesn’t Have an SMTP Proxy Matching”. Having one of the following conditions may lead to this error:

• The source mailbox isn’t stamped to have <user>@<domain>.mail.onmicrosoft.com smtp address.
• The proxy address <user>@<domain>.mail.onmicrosoft.com is not synced to Microsoft 365 on the corresponding cloud mail-user object.

Error Brief: The error occurs when the destination mailbox lacks the required routing proxy address {<domain<.mail.onmicrosoft.com }. It prevents Exchange from correctly mapping source & target accounts.

Resolved Mailbox Migration Error: Know How?

This section will help you identify if the mail is missing from the on-premises server or the online server. Then, it will discuss the concise manual methods to fix Target Mailbox Doesn’t Have an SMTP Proxy Matching Error. If the upcoming process reveals that the mail is present in both servers offline and online, then you are facing a synchronization issue between the servers.

To remove the error we must make sure the availability of the missing email address in both the source and destination Exchange server mailboxes. We can achieve this through the Exchange Management Shell (EMS) or the Exchange Admin Center (EAC).

Find the source of error:

To find it, we must run the following commands on the on-premises server and the online server.

Run the following cmdlet on the Exchange Management Shell:

• Get-Mailbox <AffectedUser> | FL EmailAddresses, EmailAddressPolicyEnabled

Run the following cmdlet on Exchange Online PowerShell:

• Get-MailUser <AffectedUser> | Select -ExpandProperty emailaddresses

Note: Replace the <AffectedUser> with the user facing the issue. And remember to do the same for all the upcoming commands.

Once you find the source of the error, then, as per the state, follow the upcoming sections. State 1 will address the absence of mail in Exchange on-premises, while State 2 will address the solution for mail missing in Exchange Online.

State 1. Mailbox is missing from Exchange On-premises

We must add <user>@<<domain>.mail.onmicrosoft.com email in the Exchange on-premises mailbox to fix Target Mailbox Doesn’t Have an SMTP Proxy Matching error. However, here also we have 2 conditions and will discuss each one below.

Condition 1. EmailAddressPolicyEnabled is True

It indicates that the on-premises mailbox has an email address policy. Now, follow the steps to make sure that the on-premises mailbox has an SMTP address that matches <user>@<<domain>.mail.onmicrosoft.com:

1. Open the Exchange Admin Center on the on-premises Exchange server.
2. Click Mail flow, and then click Email address policies.
3. Select the email address policy that you want to change, and then click Edit.
4. In email address format, add the domain (a<domain>.mail.onmicrosoft.com) to the policy, click Save, then click Apply to save the change to the recipients.
5. To verify the update, run the cmdlet:
   Get-Mailbox <AffectedUser> | FL EmailAddresses

Condition 2. EmailAddressPolicyEnabled is False

In this condition, you must also manually include the .mail.onmicrosoft.com email address, like before, but with a different procedure. Follow the steps below to add the email:

1. Open the Exchange Admin Center on the on-premises Exchange server.
2. Click recipients, and then click mailboxes.
3. Select and double-click the on-premises mailbox that you want to change.
4. In email addresses, click the add icon () to add SMTP address that matches <user>@<<domain>.mail.onmicrosoft.com.
5. Click OK, and then Save.
6. Verify the changes by running the following command:
   Get-Mailbox <AffectedUser> | FL EmailAddresses, EmailAddressPolicyEnabled

State 2. Email address missing from Exchange Online

If you are missing the email template <user>@<<domain>.mail.onmicrosoft.com from the Exchange Online, then you can run the cmdlets below to get information for resolving the issue.

• Users using the MSOnline (MSOL) service PowerShell module use the following command to retrieve information regarding any errors with a user account:
  • (Get-MsolUser -UserPrincipalName <AffectedUser>).Errors.ErrorDetail.ObjectErrors.ErrorRecord.ErrorDescription
• User using the Microsoft Entra ID PowerShell module, use the following command to retrieve information regarding any errors with a user account:
  • (Get-AzureADUser -ObjectId <AffectedUser>).Errors.ErrorDetail.ObjectErrors.ErrorRecord.ErrorDescription

Note: In both the cmdlets, replace the <AffectedUser> with the user for whom you are getting the SMTP error.

Now we will check if <user>@<<domain>.mail.onmicrosoft.com email is present in Microsoft 365 with the following cmdlets:

Again, for users utilizing the MSOnline (MSOL) service PowerShell module, use the following command:

And for users with the Microsoft Entra ID PowerShell module, use the following command

The above two commands will return the proxy address associated with the user specified.. In the proxy address list, look for <user>@<<domain>.mail.onmicrosoft.com. If it’s in the list, then the email is present online, but due to a synchronization issue, it is not updated in Exchange. Resynchronization will resolve the issue.

Common ways to fix Target mailbox doesn’t have an SMTP Proxy Matching error

Try out the basic fixes to handle the issue correctly:

• Recreate the target mailbox.
• Verify the mailbox mapping file.
• Check the domain configuration.
• Run directory synchronization.
• Add missing SMTP Proxy addresses.
• Verify SMTP addresses in the Target mailbox.

How to check for directory sync errors?

Try out the given cmdlet to find directory sync errors:

• Run the following PowerShell cmdlet to check whether the user object in Microsoft Entra ID has a validation error or not:
  Install-Module -Name Microsoft.Entra
  Connect-Entra -Scopes ‘User.Read.All’
  (Get-EntraUser -Filter “startsWith(DisplayName, ‘<user display name>’)”).serviceProvisioningErrors.errorDetail
• Run the following PowerShell cmdlet to check whether the user object in Microsoft Entra ID has an SMTP address that matches <user>@<<domain>.mail.onmicrosoft.com:
  (Get-EntraUser -Filter “startsWith(DisplayName, ‘<user display name>’)”).ProxyAddresses

There might be a sync issue if the user object in Exchange Online doesn’t have a SMTP address that matches <user>@<<domain>.mail.onmicrosoft.com, but the user object in Microsoft Entra ID does.

Best practices to prevent the migration error

Follow the provided practices to reduce the chances of migration errors in the future:

• Maintain accurate email address mapping.
• Do not change naming conventions frequently.
• Perform pre-migration checks, as it brings extra safety.
• Monitor synchronization between Active & cloud directory.
• Validate domains in advance to avoid migration disruptions.

Conclusion

Abrupt termination of a migration job can lead to data loss if not handled correctly. The solution mentioned in this article will help you to fix mailbox migration error “Target Mailbox Doesn’t Have an SMTP Proxy Matching”. However, if for any reason the issue persists, you must seek assistance from a professional tool for a seamless migration. Recoveryfix for Exchange Server is a tool empowered with advanced features that can facilitate an accessible migration of Exchange and aid in Exchange EDB file recovery.

• Export mailbox items to PST, EML, and MSG.
• User-friendly interface for improved accessibility.
• Recover deleted Exchange mailboxes and public folders.
• Migrate mailbox items to Office 365, Outlook profile, and Live Exchange.

Free Download

FAQs: Get Quick Answers

Q 1- How do directory synchronization problems trigger the migration error?

A- It prevents proxy addresses from syncing between on-premises Exchange & Exchange Online, which can trigger the migration error.

Q 2- Why do only some mailboxes show the SMTP proxy mismatch error?

A- It is noticed that certain mailboxes may not inherit email address policies. As a result, it leaves the required routing addresses missing during migration.

Q 3- What role can the administrators play to avoid the SMTP proxy error before migration begins?

A- They can perform certain things, like audit mailbox attributes, confirm accepted domains, & verify proxy address synchronization.