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Exchange Mailbox Migration Errors

This article includes a list of errors that may arise during an Exchange mailbox migration, as well as steps for resolution and any additional details.

 

​​​'>' is an unexpected token

Error message

​​​'>' is an unexpected token

Explanation

This error means that we tried to connect to Exchange Web Services (EWS) but received a redirect to another page such as an OWA web page. Instead of receiving a web service XML payload , we received an HTLM payload which results in this "unexpected token" error. This typically indicates that the server does not implement EWS and that we are unable to authenticate to the server.

Resolution

We recommend the following:

  1. Review the error message to determine if the error originates from the source or destination.
  2. Check the Exchange version used by the corresponding source or d​estination Exchange endpoint.
  3. If it is Exchange 2003, EWS is expected to be unavailable. Check credentials by logging in to OWA.
  4. If it is Exchange 2007, 2010, 2013, or 2016, EWS is expected to be available. Check EWS acce​ss by performing the following:
    1. Verify access​

404 Authentication Errors in Exchange 2003

Explanation

When migrating from Exchange 2003 servers, we have seen a few cases where, if using Forms-Based Authentication, migrations report 404 errors when attempting to authenticate.

Resolution

Disable Forms-Based Authentication before starting your migration.​

404 Resource Not Found

This error can occur for a number of resource issue.

Mailbox Not Found

  • If you are encountering this error message during credentials validation, the email address does not correspond to the primary SMTP address of a mailbox.

Folder Not Found

  • If you are encountering this error message in the middle of a migration, the folder we pr​eviously discovered was renamed or deleted.

Item Not Found

  • If you are encountering this error message in the middle of a migration, the item we previously discovered was renamed or deleted.

Resolution

Mailbox Not Found​

  • Follow the steps in this guide for verifying the account credentials.

Folder Not Found

  • Resubmit the migration in Retry Errors mode, which can be found in the drop down menu with the different migration types. MigrationWiz will discover the new changes and continue from where it left off.

Item Not Found

  • ​Resubmit the migration in Retry Errors mode, which can be found in the drop down menu with the different migration types. MigrationWiz will discover the new changes and continue from where it left off.

405 Method Not Allowed

Error message

405 Method Not Allowed

Explanation

Most Exchange servers are configured to accept standard HTTP requests of type "GET" or "POST". However, the Exchange Web DAV protocol also uses other methods such as "PROPFIND", "SEARCH", or "X-MS-ENUMATTS". Those methods (also known as verbs) may be blocked by your IIS configuration.

Resolution

If migrating from Exchange 2007, check which verbs are allowed in your IIS Exchange configuration and ensure methods listed above are allowed.​

440 Login Timeout

Error message

440 Login Timeout

Explanation

The credentials used to access the mailbox configured is invalid, or the credentials specified do not have access to to the configured mailbox, or you may be have over-utilized resources.

Resolution

Invalid Credentials

The most common p​roblem when encountering this error is that the user name and password specified is not able to access the mailbox. You can verify that the user name and password is correct by testing mailbox access using OWA. If your connector is set to use administrative access, make sure to log in to the mailbox using administrator credentials (since this is what MigrationWiz will do).​

If you have verified that the credentials are correct, enter the credentials into MigrationWiz, and resubmit the mailbox for migration.  It may be possible that the credentials were specified incorrectly.

Over-utilized Resources

If you have verified that your credentials are working properly, it's possible that you may have over-utilized resources. 

The first thing to do is attempt to open your OWA URL from an external network from a system that is not joined to your domain.  If OWA is loaded in a timely manner, check your server resources:

  1. Check server CPU usage
  2. Check memory usage
  3. Check disk I/O usage using performance monitor
  4. Check for over-utilization of network

The most common problem encountered is the over-utilization of network. This means that you are attempting to migrate too many mailboxes simultaneously, and do not have enough bandwidth to execute them.

TLS Settings

MigrationWiz only supports TLS 1.2 at this time. If the endpoint only allows TLS 1.0, it will need to be updated to allow TLS 1.2.

500 Internal Server Error

Error message

500 Internal Server Error

Explanation

This is a generic error that is returned by Exchange.

Resolution

Check the event logs on both the Client Access Server (CAS) and Mailbox Server for events that correlate to the errors logged by MigrationWiz.

​​​503 Service Unavailable

Error message

​​​503 Service Unavailable

Explanation

The service that hosts the Exchange server process is not accessible.

Resolution

Check the event logs on both the Client Access Server (CAS) and Mailbox Server for events that correlate to the errors logged by MigrationWiz.

You may also want to try and restart the Exchange services and/or reboot the server to see if the problem is corrected.

If you are migrating to Microsoft 365, this error indicates Microsoft 365 had a temporary, limited outage. Please wait 24 hours and resubmit your mailboxes for migration.​

507 Insufficient Storage

Error message

507 Insufficient Storage

Explanation

By default, Exchange Server has message size limits of 10MB. Although the Exchange server may accept delivery of items larger than 10MB via SMTP, MigrationWiz migrates email using EWS, which is subject to different size limits.

Resolution

You can confirm that you have exceeded the server size limits:

  1. Sign in to your MigrationWiz account
  2. Click on the checkbox next to the mailbox in question.
  3. On the dashboard, click on the Start button.
  4. Click on the Start Migration button.
  5. Click on the red number listed in the Errors column.
  6. Review the information listed under the migration errors field, and correct it using the appropriate resolution steps specified in the product content for Exchange Server and Office 365 below.

If the average error size is greater than 10MB, you have most likely hit message size limits imposed by Exchange Server.

Increase Message Size Limits

This is a two-step process. The reason for this is that if the message size limits of Exchange are increased, the IIS limits will also have to be increased to allow increased payloads. There are other non-standard settings that can also cause size restrictions for the IIS or EWS connections, but we are unable to troubleshoot or identify specific environment restrictions outside of these settings.

To display current message size limits:

  1. Open the Exchange Management Shell.
  2. Enter the following commands:

Get-TransportConfig | Format-List -Property MaxReceiveSize, MaxSendSize
Get-SendConnector | Format-List -Property Identity, MaxMessageSize
Get-ReceiveConnector | Format-List -Property Identity, MaxMessageSize
Get-MailBox | Format-List -Property PrimarySmtpAddress, MaxSendSize, MaxReceiveSize

To increase message size limits on the Exchange Server:

  1. Open the Exchange Management Shell.
  2. Enter the following commands:

Set-TransportConfig -MaxReceiveSize 150MB -MaxSendSize 150MB
Get-SendConnector | Set-SendConnector -MaxMessageSize 150MB
Get-ReceiveConnector | Set-ReceiveConnector -MaxMessageSize 150MB
Get-Mailbox | Set-Mailbox -MaxSendSize 150MB -MaxReceiveSize 150MB

 

Increase IIS Limits to Allow Accepting Payloads

There are three limits that should be increased in IIS:

  • maxRequestLength
  • maxAllowedContentLength
  • maxReceivedMessageSize

Follow these steps to increase the Exchange message size limits on your client access server:

  1. OpenWindows Explorer.
  2. Navigate to %ExchangeInstallPath%FrontEnd\HttpProxy\ews\
  3. Open the file Web.Config in a text editor, such as Notepad.
  4. Find the XML tag starting with for each change.
  5. Change the existing value to maxRequestLength="200000" -- this occurs in one place in the Web.Config file.
  6. Change the existing values to maxAllowedContentLength="200000000" -- this occurs one place in the Web.Config file.
  7. Change the existing values to maxReceivedMessageSize="200000000" -- this entry occurs up to 12 times. This needs to be changed for each Authentication method.
    For example:
    <httpsTransport maxReceivedMessageSize="200000000" authenticationScheme="Anonymous" maxBufferSize="81920" transferMode="Streamed" />
    <httpsTransport maxReceivedMessageSize="200000000" authenticationScheme="Basic" maxBufferSize="81920" transferMode="Streamed" />
    etc.
  8. If you are running IIS7 and Windows 2008, it may be necessary to increase WCF settings.
  9. Save the file.
  10. IIS Reset is not needed, web.config changes are picked up by the next connection.

Follow these steps to increase the Exchange message size limits on your mailbox server:

  1. OpenWindows Explorer.
  2. Navigate to %ExchangeInstallPath%ClientAccess\exchweb\ews\
  3. Open the file Web.Config in a text editor, such as Notepad.
  4. Find the XML tag starting with for each change.
  5. Change the existing value to maxRequestLength="200000" -- this occurs in one place in the Web.Config file.
  6. Change the existing values to maxAllowedContentLength="200000000" -- this occurs one place in the Web.Config file.
  7. Change the existing values to maxReceivedMessageSize="200000000" -- this entry occurs up to 12 times. This needs to be changed for each Authentication method.
  8. If you are running IIS7 and Windows 2008, it may be necessary to increase WCF settings.
  9. Save the file.
  10. IIS Reset is not needed, web.config changes are picked up by the next connection.

For more information about message size limits on Exchange Server:

​An existing connection was forcibly closed by the remote host​

Error message

​An existing connection was forcibly closed by the remote host​

Explanation

This error message may occur when migrating a large item (containing large attachments, for instance). ​The Destination system will keep a connection open only for so long, after which the connection will be closed (timeout).

Resolution

If the destination server's configuration is under your control:

  1. Increase the connection timeout for incoming data transfers.
  2. Increase the size limit of items that can be created through the API.

Auto-discovery services suggest URL error

Error message

Auto-discovery services suggest URL

Explanation

This error indicates that we were unable to connect to the Source system using the Source URL specified on your connector. We then queried Exchange auto-discover services, which responded with an suggested URL. This error message is asking you to check if the suggested URL is correct and, if so, to update your configuration.

Resolution

Check if the suggested URL points to the Source. For example, if auto-discover settings already point to the Destination system, then the suggested URL will be incorrect as a Source URL, and so should not be used. Otherwise, try specifying the suggested URL on your connector as the Source URL and resubmit mailboxes for migration.

Connection did n​ot succeed. Try again later.

Error message

Connection did n​ot succeed. Try again later.

Explanation

This error may occur for the following reasons:

  • ​Mailbox Permissions. The admin account used to migrate multiple mailboxes is not a global admin, or it does not have a mailbox you can log in to using OWA, or it has insufficient permissions.
  • Connection Throttling. The admin account was used to migrate multiple mailboxes, and Exchange throttled concurrent connections. For example, Microsoft 365 will only allow 10 concurrent connections per admin account.
  • Mailbox Provisioning.  A mailbox was provisioned shortly before initiating migration, and the mailbox wasn't fully available. For example, Microsoft 365 will frequently return this error if a mailbox is submitted immediately after provisioning, due to data center replication delays.
  • Excessive Server Load. The target server was under an excessive load, and so started returning this error. For example, Microsoft 365 servers usually experience high load at specific times such as Fridays (evenings) or Mondays (mornings).

Resolution

We recommend trying the following:

  1. In many cases, replication or server load issues are resolved simply by waiting a few minutes.
  2. If using administrative credentials, using impersonation will likely resolve the issue.
  3. Check the admin account:
    1. Make sure it is a global admin (Microsoft 365).
    2. Make sure it has a mailbox that can be logged in to (use OWA).
    3. Consider granting explicit permissions to all mailboxes.
      1. Office 365 instructions
      2. Exchange 2010 instructions
  4. Check throttling limits:
    1. Office 365 instructions
    2. Exchange instructions
  5. Decrease the number of simultaneous migrations. The default Exchange 2010 limit is 10.
  6. Consider creating more than one connector, each using a different admin account.
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