Outlook is unable to connect to the proxy server auto discover

Outlook is unable to connect to the proxy server auto discover who upgraded to Windows 11 reported that some versions of Outlook, including Outlook for Microsoft 365, no longer connected to their internal Exchange server with the error message Outlook is unable to connect to the proxy server auto discover. This post provides the most applicable solutions to the issue. The error message When this issue occurs, you will receive a full error message with an error code.

Read also: Your Outlook account settings are out of date in Mail or Calendar app

Microsoft Outlook

  • There is a problem with the proxy server’s security certificate.
  • Outlook is unable to connect to the proxy server autodiscover. (Error Code 80000000).

Outlook is unable to connect to the proxy server auto discover

If you are facing the Outlook is unable to connect to the proxy server auto discover issue on your Windows 11/10 device, you can try our recommended solutions below in no particular order to resolve the issue on your system. Method 1: Restart your computer

  1. Initial checklist
  2. Turn on TLS 1.0 on the local Windows 11 machine
  3. Add TLS 1.2 to the Exchange server
  4. Upgrade Exchange Server

Let’s take a look at the process involved concerning each of the listed solutions.

1] Initial checklist

Before you try the solutions below, you can do the following and after each task see if Outlook can now connect to the email server autodiscover without issues:1. Check your internet connection and make sure that you can access other websites.

  • Check compatibility of Outlook client with Exchange server version. For example, Microsoft 365 is not supported by Exchange 2010. Installing the corresponding compatible Outlook client, such as Outlook 2013, may resolve issues experienced when using Microsoft 365 with Exchange 2010. Additionally, logging in to Outlook Web App (OWA) can help confirm if the issue is related to the Outlook client.
  • To check if the Autodiscover service is running, follow the instructions in this post. In addition, make sure your PC is not experiencing internet connectivity issues and that the Exchange server is not offline.
  • On-premises users can run Microsoft Remote Connectivity Analyzer to connect to Office 365, and Office 365 users can run Microsoft Support and Recovery Assistant to diagnose and fix problems with their Office 365 account.
  • Adding your Exchange server’s MX name/record to the proxy exclusion list may help. You can also try using a VPN locally on your network.

2] Turn on TLS 1.0 on the local Windows 11 machine

More of a workaround than a solution, this action is not recommended because TLS 1.0 is retired and should be moved away from. Nevertheless, if you need an immediate resolution to the issue, you can enable or turn on TLS 1.0 via the registry on the local Windows 11 machine. Do the following:

Since this is a registry operation, it is recommended that you back up the registry as a precautionary measure. Once done, you can proceed as follows:

  • To invoke the Run dialog, press the Windows key + R.
  • In the Run dialog box, type “regedit” and hit Enter to open Registry Editor.
  • Use “Navigate to the registry key path below:” or “Jump to the registry key path below:”

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp

  • At the location, double-click the DefaultSecureProtocols entry on the right pane to edit its properties.

If a registry key is not present, right-click on the blank space on the right pane, select New > DWORD (32-bit) Value, and then rename the key accordingly.

  • Click on the new entry to edit its properties.
  • 00000080 in the Value data field.
  • To save the change, click OK or hit Enter.
  • Next, repeat the steps below at the registry path:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp

  • Exit Registry Editor when done.
  • Restart computer.

3] Add TLS 1.2 to the Exchange server

Windows 11 disables TLS 1.0 and TLS 1.1 by default, which affects Exchange 2010 running on Windows 2008 R2 that uses TLS 1.0. As reported in some cases, the issue started when the Windows 10 client machines were upgraded to Windows 11 and the issue is only noticed on workstations connected outside of the subnet the server is connected to. That is, all of the workstations connected to the same subnet as the server were working fine after the Windows 11 upgrade, but all of the workstations outside of that subnet failed with proxy (Error Code 80000000).

This workaround uses TLS 1.2 by default to safely connect to Exchange servers. IT admins just need to add TLS 1.2 to the Exchange servers and reboot the server afterward. Windows 11 supports TLS 1.2 by default.

Below are the registry keys that can be added to Command Prompt:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client]

Added DWORD: DisabledByDefault = 00000000 (0)
Added DWORD: Enabled = 00000001 (1)

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]

Added DWORD: DisabledByDefault = 00000000 (0)
Added DWORD: Enabled = 00000001 (1)


Added DWORD: SystemDefaultTlsVersions = 00000001 (1)


Added DWORD: SystemDefaultTlsVersions = 00000001 (1)

4] Upgrade Exchange Server

The Exchange Server 2010 reached its end of support on October 13, 2020.It is recommended that you upgrade your Exchange server to a newer version by your Internet Service Provider (ISP) or company email server or IT administrator. After the Exchange upgrade, you can upgrade and reinstall the latest version of Outlook client for Windows 11/10.

Why does Outlook say Unable to connect to proxy server?

This issue may occur if one or more of the following conditions are true:

  • The server requires a certification authority (CA) for the connection.
  • You haven’t trusted the root certification authority.
  • The certificate may have been revoked.

What does proxy email mean?

A mail proxy server is a machine that is located in front of an email server. It can provide services such as web-based email via IMAP.

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