There is a problem with the proxy server's security certificate - Outlook

You may receive the error message In that location is a trouble with the proxy server's security document when Outlook tries to connect to a server by using an RPC connection or an HTTPS connection. In this post, we volition identify the potential causes, every bit well equally offer the most acceptable solutions to resolve this outcome.

There is a problem with the proxy server's security certificate

When you come across this upshot, you lot'll receive the post-obit full fault message;

In that location is a problem with the proxy server's security certificate.
The name on the security certificate is invalid or does not match the proper noun of the target site webmail.domain.com.

Outlook is unable to connect to the proxy Server. (Error Code 0)

Possible variants of the error message with accompanying error lawmaking when the fault occurs tin be any of the following;

At that place is a problem with the proxy server'south security certificate, %s. Outlook is unable to connect to this server.
There is a problem with the proxy server's security certificate, %southward. The proper noun on the security document is invalid or does not match the name of the site. Outlook is unable to connect to this server.
There is a problem with the proxy server's security certificate, %south. The security document is not from a trusted certifying authorization. Outlook is unable to connect to this server.

According to Microsoft documentation, this issue may occur if 1 or more of the following weather condition are true:

The connection to the server requires a certification authority (CA).
You oasis't trusted the certification authority at the root.
The document may exist invalid or revoked.
The certificate doesn't friction match the proper noun of the site.
A tertiary-party add together-in or a third-party browser add together-in is preventing access.

There is a problem with the proxy server's security certificate – Outlook error

If y'all're faced with this event on your Windows eleven/10 PC, you can try our recommended solutions below in no particular order and run across if that helps to fix the Outlook error message In that location is a problem with the proxy server's security certificate.

Check Proxy server certificate
Install the trusted root certificate
Disable third-party addition in Outlook
Disable third-party browser add together-ins
Manually configure Exchange Proxy Settings in Outlook

Let'southward take a look at the description of the procedure involved concerning each of the listed solutions.

ane] Cheque Proxy server certificate

Check Proxy server certificate

This solution requires you to check the document, and and so contact your arrangement ambassador to resolve this In that location is a problem with the proxy server'south security certificate effect.

To check the proxy server certificate, do the following:

Open up Border browser on your Windows 11/ten PC.
Type or copy and paste the URL below into the address bar of the web browser and hit Enter. Replace the server_name placeholder with the RPC server name or the secure server name.

https://www.server_name.com/rpc

Next, click the padlock icon on the address bar.
On the flyout, click Connection is secure.
Click on the Security Certificate icon to view the Security Document.
In the Security Certificate properties sheet, click the Details tab.
Now, brand a note of the information in the fields highlighted on the image in a higher place.

TheValid to field should betoken the date until which the certificate is valid. The data in the Subject field should match the site name – and if this is not the case, contact your IT administrator.

2] Install the Trusted Root Certificate

This solution requires you to install the Trusted Root Document on the Windows 11/10 client computer.

Do the following:

When the mistake occurs and you're prompted with theCertificate dialog box, click Install Certificate.
ClickNext.
Click to select thePlace all certificate in the following shop check box.
ClickBrowse.
ClickTrusted Root Certification Authorities.
Click OK.
ClickNext.
ClickEnd.
ClickOK.

iii] Disable third-party add together-on in Outlook

Another feasible solution to gear up the fault in view is to disable third-party add-in in Outlook. To exercise this, yous beginning need to starting time Outlook in Safety Mode, and if Outlook successfully opens in Safe Mode, then information technology'southward likely the error is triggered by third-party add-ons.

To disable third-party COM add-ins in Outlook, do the following:

Start Outlook in Condom Style.
On theFile carte, clickOptions >Add together-Ins.
In theManage box, clickCOM Add-ins >Go.
At present, uncheck the box for the third-party add-ins that you want to disable.
Restart Outlook.

iv] Disable third-party browser add together-ins

Depending on your browser, this solution requires you to disable third-party browser add-ins and see if that helps to resolve the issue. Otherwise, attempt the side by side solution.

5] Manually configure Commutation Proxy Settings in Outlook

Manually configure Exchange Proxy Settings in Outlook

To manually configure Commutation Proxy Settings in Outlook, do the following:

Open Microsoft Outlook.
Navigate to Account Settings >More Settings >Connection >Exchange Proxy Settings.
Now, type in the address beneath into the Simply connect to proxy servers that have this principal name in their document field.

msstd:webmail.domain.com

Click OK.

Alternatively, to reach the aforementioned result, practice the post-obit:

Printing Windows key + X to open Ability User Menu.
Tap A on the keyboard to launch PowerShell in admin/elevated mode.
In the PowerShell panel, type in or re-create and paste the command below and hit Enter.

Gear up-OutlookProvider EXPR -CertPrincipalName:$nothing

Exit PowerShell when the cmdlet executes.

That'southward it!

Related post: Error 0x80004005, The Performance Failed in Outlook

Why is my Outlook non trusted?

If you accept encountered the Outlook.com security certificate fault or the mistake message The server you are connected to is using a security certificate that cannot be verified – the well-nigh common reason behind this error is that you accept the wrong hostname configured in Microsoft Outlook.

Read: Your Outlook account settings are out of appointment in Post or Calendar app.

Why am I getting a security certificate alert?

The reason why you lot might be getting a security document warning on your Windows eleven/x PC is due to incorrect date and time. Security certificates are used by web browsers and computers to make sure a particular site is safe. So, if your computer has the wrong engagement and time, it can cause certificates to appear invalid & your spider web browser will begin to upshot security warnings. So, make sure the date and time is right on your reckoner.

How do I get rid of security certificate errors?

To get rid of security certificate errors on Windows 11/10, you demand to disable this pick. Follow these instructions:

Open Control Console.
Select Internet Options.
Click the Advanced tab.
Scroll down to the Security section.
Under the Security section, uncheck the Warn near certificate address mismatch choice.
Click Apply > OK to salvage the changes.
Reboot your PC.

Why is my electronic mail certificate not trusted?

The nigh likely reason your email certificate is not trusted is due to incorrect email settings. When you're getting a document not secure error message for your e-mail, information technology is considering you lot've synced an email business relationship that belongs to you or your organization domain, merely there's a mismatch in the SMTP/IMAP settings, port settings, or domain name settings.