401.5 Access Denied when verifying EAS and autodiscover URL


The following error is presented within the MailEnable Activesync management tool when performing a verification test:

Executing Test: ActiveSync Support...

The remote server returned an error: (401) Unauthorized.
Suggestion: The IIS virtual directory configuration is invalid. Please ensure that only Anonymous authentication is enabled for the virtual directory (specifically, Windows Authentication should be disabled).

Using an Internet browser to test the ActiveSync service or autodiscover service URL the following is presented:

HTTP Error 401.5 - Access Denied

The URL you tried to reach has an ISAPI or CGI application installed that verifies user credentials before proceeding. This application cannot verify your credentials.


Autodiscovery is a mechanism by which desktop and mobile mail clients can resolve a user's email address (and password), to return connection settings.

There are two types of Autodiscovery requests: Desktop (IMAP, SMTP, etc) and Mobile (Microsoft Exchange ActiveSync).

Clients supporting Autodiscovery will use the domain portion of the e-mail address to query an autodiscovery HTTP host URL (typically https://example.com/autodiscover/autodiscover.xml).

The server will validate the email address and password combination and return connection information for the client.


If the above-mentioned 401.5 error is returned, it is likely that Basic Authentication and Digest Authentication methods are disabled under the "Synchronization Service" properties within the MailEnable Management Console.

Note: These settings are enabled by default but may have been disabled via the MailEnable Management Console (either deliberately or accidently without knowing the implications of doing so).


To resolve this issue you will need to ensure that the correct authentication settings are defined for autodiscovery. This can be done as follows:

  1. Open the MailEnable Administration Console and navigate to: Servers > localhost > Services and Connectors > Synchronization.
  2. Right click on "Synchronization" and select properties.
  3. Under the "General" tab tick the options for "Basic Authentication" and "Digest Authentication".
  4. Restart the Synchronization Service and IIS.


Online Verification Tool: http://www.mailenable.com/Tools/ActiveSync/Verification.asp

Product:MailEnable (All Versions)
Class:TRB: Troubleshooting (Configuration or Environment)
Revised:Sunday, February 11, 2018