The Remote Server Returned an Error (403) Forbidden Exchange 2010

In this article, I am going to discuss "The remote server returned an error (403) forbidden in Exchange Server 2010". Generally, Exchange Administrator faces this issue when they try to migrate Exchange server 2010 mailbox data into Office 365 user account.

Problem Definition

At the time to Migration of Microsoft Exchange Server 2010 to Office 365 with Hybrid deployment of server. During the migration operation fails, the error message you get that 'the remote server returned an error (403) forbidden Exchange' or 'the connection to the server "mail.mailtest.com" could not be completed'.

The first error message you get while performing the migration using PowerShell commands and the second error message we get when performing the migration with the help of Exchange Admin Center.

Cause of Error 403

The problem occurs, if the mailbox replication proxy (MRS Proxy) service is disabled on hybrid server within EWS Virtual directory. There could be some reasons cause of which the error could occur:

1. MRSProxy might be in disabled state Run below mentioned command in EMS.
   Get-WebServicesVirtualDirectory "ABCServerName\EWS (Default_Website)" |FL Server, MRSProxyEnabled
   if you get MRSProxyEnable:False then it the actual cause of Error 403
   
2. Another reason could be that on the hybrid server, MRSProxy is showing Enabled but while running the Get-WebServicesVirtualDirectory command, it is actually disabled. After running the above command, if you get True then look for the Exception message in 1309 Web Event. You will see that over there Exception Message is "MRS Proxy service is disabled"
   

Solution to fix Error 403

The remote server returned error 403 could be resolved can be resolved by two ways. The first way to fix error 403 is by enabling MRSProxy or by first disabling and then enabling MRSProxy.

Enable MRSProxy

To enable MRSProxy for fixing Error 403, first run below command and then restart IIS using iisreset command:
Set-WebServicesVirtualDirectory "ABCServerName\EWS (Default_Website)" -MRSProxyEnabled $true

First Disable and then Re-enable MRSProxy

Run below command to firstly disable and then re-enable MRSProxy:
Disable: Set-WebServicesVirtualDirectory "ABCServerName\EWS (Default_Website)" -MRSProxyEnabled $false
Enable: Set-WebServicesVirtualDirectory "ABCServerName\EWS (Default_Website)" -MRSProxyEnabled $true
Now, restart the Microsoft IIS with the help of iisreset command.

Exception Case

If the above discussed solution is not working in your case then for migration of Exchange 2010 mailboxes, you can export Exchange mailboxes to PST files first and then import those mailboxes into Office 365.

Conclusion

This article is written for providing the information regarding fixing "the remote server returned error 403" or "the connection to the server 'mail.mailtest.com' could not be completed". We discussed the multiple cause of error occurrence and what could be the possible way for resolving Error 403 in Exchange server 2010.