Functional versions of Office-Outlook?

Problem reported by Mark Thornton - 10/7/2025 at 10:44 AM

Submitted

I'm being asked to upgrade from Office 2016 and it's associated Outlook to something more current because, well that's what they want...

Office 2019, 2021, 2024? Do the registry hacks still apply? Which are still relevant? Do later versions know to look at the 16.0 registry key for these settings, or do we need to place them in the current version registry settings?

I am also confused seeing some recent posts suggesting "PreferLocalXML" should be set to 1 and referencing a local xml file, but I can't find an example of what the local xml file should contain to make it useful.

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover]

"PreferLocalXML"=dword:00000000

"ExcludeLastKnownGoodURL"=dword:00000001

"ExcludeExplicitO365Endpoint"=dword:00000001

"ExcludeHttpRedirect"=dword:00000001

"ExcludeHttpsRootDomain"=dword:00000001

"ExcludeScpLookup"=dword:00000001

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover\RedirectServers]

"autodiscover-s.outlook.com"=hex(0):

"autodiscover.hotmail.com"=hex(0):

"autodiscover.smartermonitor.com"=hex(0):

"autodiscover-s.partner.outlook.cn"=hex(0):

"autodiscover-s.outlook.de"=hex(0):

"autodiscover-s.office365.us"=hex(0):

4 Replies

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Brian Bjerring-Jensen - VonBjerring GmbH Replied

10/7/2025 at 10:51 AM

We run the 2021 LTSC version for our clients. 2024 has issues with firewall rules triggering because of unusual fast and many connections at once. And it keeps going banging on the server all the time.

J. LaDow Replied

10/7/2025 at 11:10 AM

We have several 2021 Pro Plus installs that use (Classic) Outlook - connecting via IMAP/SMTP with autodiscover works without intervention if your autodiscover is setup right.

It took a while to get our autodiscover setup just right with DNS and so forth, but once done - we didn't need to make registry changes for our clients to connect.

We don't use MAPI/Exchange though -- and no (New) Outlook installs.

MailEnable survivor / convert --

drew2160fl Replied

10/8/2025 at 1:39 PM

We too have found the sweet spot for 2021 Pro Plus Outlook installations. 2024 has some strange (sometimes not repeatable) errors. Regarding 2021, aside from some small oddities, all seems to work well.

Oh, and yes, we TOO have to change the registry settings as stated by Mark.

Douglas Foster Replied

10/8/2025 at 6:50 PM

This post from 4 years ago has the format of the XML file in the first entry

https://portal.smartertools.com/community/a93872/streamlining-autodiscover.aspx

But as my final post in that topic indicates, I quickly switched to using the registry key, because it was easier to deploy and control using Group Policy. The main issue is to disable the Office365 option and the SCP options in the registry.

The forum article has a recap of what each registry option does, and has links to my source material.

We are also running Office2021 and all of these configuration options still apply.

One problem with Office2021: It will download and activate New Outlook during Windows Updates. It will not actually work after initial install, because you have to configure a new profile. A web search will show several ways to disable it. On the machine where it happened to me, I used the option of uninstalling from the Settings... Apps page.

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