Security alert when Outlook start

Question

Hello

We migrated to o365 few years ago.No on-prem Exchange server.

Outlook test em,ail result show that everything is pointing to O365.

Recently some staff report they receive this warning:

in our DNS server , webmail.xxxx.com has a static record to IP 123.123.123.xxx (I think this is for our previous on-prem Exchange Server)

But this IP is now reused by another system host xxx1p01 (which is not a email server).

I would like to ask for help for how to suppress this warning?

Just remove the DNS statis record for webmail.xxxx.com? Or modify the Exchange Online setting ?

Thanks .have a nice day

Answer 1

Hi, Jero Cheng

It sounds like the issue you are experiencing is related to a security certificate error in Outlook.

This error message usually appears when the certificate used by the mail server is not trusted by the client computer

Here are the steps you may try.

1.Exit all Microsoft Office applications.

2.Start Registry Editor.

3.Locate and then select the following registry subkey:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\HTTP

4.On the Edit menu, point to New, and then select DWORD Value.

5.Enter FailAllCertificateErrors, and then press Enter.

6.In the Details pane, press and hold (or right-click) FailAllCertificateErrors, and then select Modify.

7.In the Value data box, enter 1, and then select OK.

8.Exit Registry Editor.

More information can be found Outlook 2016 displays a prompt that lets you connect to an Exchange server if a certificate issue occurs - Microsoft Support