Redemption on Windows Server 2019 with RDS (terminal server)

Question

I'm experiencing a strange issue with Redemption in a RDS setup. When running Outlook as an ordinary user I get the following exception when attempting to connect to the session:

System.Runtime.InteropServices.COMException (0x8000FFFF): Interface not supported at Redemption.IRDOSession.set_MAPIOBJECT(Object Value)

However, when running Outlook as Administrator (but with the same Exchange mailbox) there is no error and everything works. I have tried both with Exchange cached mode enabled and without, this does not seem to make any difference.

The C# code is like this: ... RDOSession session = RedemptionLoader.new_RDOSession(); session.MAPIOBJECT = applicationObject.Session.MAPIOBJECT; ...

Versions: Windows Server 2019, version 1809. Outlook 2019 MSO (16.0.10386.20017) 64-bit. Redemption 5.5.0.3218.

Any ideas would be welcome :)

Is this inside an Outlook addin? Or a standalone app? In the former case, is this being done on a secondary thread? — Dmitry Streblechenko, May 24 '22 at 15:18
Hi Dmitry. The code is running inside an Outlook addin. I'm wondering if the ordinary user is missing some permission wrt. the mailbox, but normal Outlook usage seems to work fine. — SoerenH, May 25 '22 at 07:43
But is your code running on the main Outlook thread or on a secondary thread? — Dmitry Streblechenko, May 25 '22 at 15:05

score 0 · Answer 1 · answered May 25 '22 at 20:05

0

Do not access applicationObject.Session.MAPIOBJECT on a secondary thread in your VSTO addin. Save its value on the main thread in a dedicated variable/member field, and use that variable on the secondary thread to set RDOSession.MAPIOBJECT property - this way only IMAPISession MAPI interface is marshaled, but not the Application OOM object (which does not like it).

answered May 25 '22 at 20:05

Dmitry Streblechenko

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Thanks Dmitry, I'll give it a try. – SoerenH May 30 '22 at 10:12

score 0 · Answer 2 · answered Jun 03 '22 at 12:29

Setting MAPIOBJECT on the main thread did not fix the error. However, deleting Registry key

"HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers\Microsoft Windows MAPI Preview Handler"

fixed it.

In my initial question I forgot to mention (sorry), that just before the Redemption exception there was a "Microsoft Office Outlook" popup saying “Either there is no default mail client or the current mail client cannot fulfill the message request”. So I guess that was causing the Remption exception, even if I still haven't figured out the root cause or why it worked when running as Administrator.

Redemption on Windows Server 2019 with RDS (terminal server)

2 Answers2