Error when switching a mailbox to the Archive Manager cached mode: "Work wasn't complete succe (16124)

Error when switching a mailbox to the Archive Manager cached mode:

"Work wasn't complete successfully.

[ Client Error: SOAPCLIENT_SOAPFAULT ] [ Status Code: 500 ] [ Fault String: User is not authenticated ]"

Forms Authentication is set on the Archive Manager Web Service.

1. Open IIS Manager and right-click on Web Site (and/or virtual directory), select Properties.

2. Select the Directory Security tab.

3. Click on Edit and disable "anonymous authentication".

4. Open the Web.config files with a text editor and edit as follows:

- Find the following line: <authentication mode="Forms">
- Change the authentication mode to Windows.

As a result the line should look like this: <authentication mode="Windows">

Note: there are two web.config files located in the following directories:

C:\Program Files\Quest Software\ArchiveManager\WebService

C:\Program Files\Quest Software\ ArchiveManager\WebSite.

5. Restart IIS