Exchange Store Manager (ESM) MAPI error 80040111 after upgrading to Archive Manager 5.1.2. (4238436)

Exchange Store Manager (ESM) MAPI error 80040111 after upgrading to Archive Manager 5.1.2.

AM server : Windows server 2012 R2
AM version : 5.1.2
Exchange : 2013
SQL Server : 2012

After an upgrade of the archive manager (4.5 --> 4.8 --> 5.1.2), the following error occured:

16:31:34 ERROR: Session.OpenMsgStore:
16:31:34 MAPI error 80040111
16:31:34 Error: The information store could not be opened.
16:31:34 Component: MAPI 1.0
16:31:34 Context: 00000286
16:31:34 Statistics for this run
16:31:34 _____________________________________
16:31:34 Folders processed : 0
16:31:34 Messages processed : 0 (0 linked)
16:31:34 Attachments processed : 0
16:31:34 Errors : 1
16:31:34 Warnings : 0
16:31:34 Mailbox export complete.

The following items were implemented from this KBA (https://support.quest.com/archive-manager/kb/138049):

**Test Internal and External proxy addresses in OWA.
**There is a high probability the External works and the Internal fails due to the fact the Internal name is not on the issued certificate and Archive Manager is trying to connect via the internal address. If this error occurs after an upgrade, test by looking at wlogs prior to the upgrade to see if the ProxyServer matches the one in the logs after the upgrade.
**Workaround. The following item can be added to Configuration Console...

Item Name: Autodiscover Override Settings
Value: ProxyAuthScheme=NTLM;ProxyServer=mail.domain.com (ProxyServer item was added along with the internal Proxy address to correct the issue).

Note: Please make sure that the Proxy Server FQDN is correct, otherwise will result in a "MAPI error 80040111" as well.

Unfortunately this didn't resolve the issue.

The Archive Manager 5.1.1 Release Notes on Page 2 Point 4 (also a brief note in the Archive Manager 5.1.2 Release Notes too) states the following:

https://support.quest.com/archive-manager/technical-documents

New Default Behaviour for Exchange 2013: Autodiscover is used to automatically configure a MAPI profile to connect to Exchange 2013.
By default, Archive Manager 5.1 now uses the internal client configuration for connections to Exchange 2013.

This issue was resolved by implementing the following...

To use Autodiscover’s external client configuration, perform the following steps please:

1.   Launch Configuration Console > Advanced Settings
2.   Add the following configuration item (without the single quotes): ‘Autodiscover Use External Mailbox Server’ and set the value to True in the next cell in the same line.
3.   Restart Exchange Store Manager and Data Loader services.

If the issue still happens, then remove the Autodiscover section that was implemented in the first KBA above - example below (as maybe conflicting) and restart the Exchange Store Manager and Data Loader services again.

Workaround example from above...
The following item can be added to Configuration Console:
Item Name: Autodiscover Override Settings
Value: ProxyAuthScheme=NTLM;ProxyServer=mail.domain.com (ProxyServer item was added along with the internal Proxy address to correct the issue).