Disable Autodiscover in Office 365
We’ve been getting reports of users with their Office 365 subscription using their hosted email address (with hosting.ca). All new outlook 365 or Outlook Live accounts will automatically try to connect to Office 365 first. It would appear that you would connect to the mailbox as some @outlook.com address.
Update November 11, 2025
This is how you would disable autodiscover in the more recent versions of MS Outlook/Office 365.
Download this disable-autodiscover.reg file, and run it. It will disable the checking for other methods except SRV autodiscover.
Manual Instructions:
We have a registry key to help disable this functionality as this will fix connectivity to our hosted Exchange services.
Create a new notepad file and name it “disable-autodiscover.reg” and paste the following contents inside:
; ==========================================================
; Outlook Autodiscover Hardening for Hosted Exchange (2016/2019)
; Prevents Outlook from redirecting to Microsoft 365 endpoints.
; Works for Outlook 2016, 2019, and Microsoft 365 desktop builds.
; ==========================================================[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover]
; Skip AD SCP lookup (irrelevant in hosted environments)
“ExcludeScpLookup”=dword:00000001; Allow HTTP->HTTPS redirects (some hosts rely on them)
“ExcludeHttpRedirect”=dword:00000001; Skip HTTPS root domain (https://domain.com/autodiscover/autodiscover.xml)
“ExcludeHttpsRootDomain”=dword:00000001; Allow direct HTTPS autodiscover (https://autodiscover.domain.com)
“ExcludeHttpsAutodiscoverDomain”=dword:00000001; Allow SRV record lookup (_autodiscover._tcp.domain.com)
“ExcludeSrvLookup”=dword:00000000; **Critical**: Disable fallback to Office 365 autodiscover
“ExcludeExplicitO365Endpoint”=dword:00000001; Optional: prefer locally deployed autodiscover.xml if present
“PreferLocalXML”=dword:00000001; Disable Microsoft Account / OAuth Autodiscover prompt
[HKEY_CURRENT_USER\Software\Microsoft\Exchange]
“AlwaysUseMSOAuthForAutoDiscover”=dword:00000000
After saving it, run it to install it.
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Works for Outlook 2016/2019/365 (Office 16) — if you have older Outlook (2013), change the path
16.0→15.0. -
🔁 Applies to the current user only (
HKCU). If you want to apply it for all users on a PC, it can also be placed under:🚀 Restart Outlook after applying — it must reload autodiscover logic.
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🧹 Optional: after applying, you can delete the Outlook profile and recreate it if users are still cached to Microsoft endpoints.
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🛠 You can push this registry file by GPO, logon script, or RMM tool — it’s lightweight and reversible (just delete the keys).
The official document from MS is: https://support.microsoft.com/en-ca/help/2212902/unexpected-autodiscover-behavior-when-you-have-registry-settings-under
There is another document regarding Windows 10 users running office 2010 products as well.