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Outlook is unable to connect to the proxy server

I tried to setup RPC over HTTP. Setup GoDaddy security certificate, evrythihg look OK, but clients can't connect Exchange server.
Message: "Outlook is unable to connect to the proxy server. (Error Code 10)
Please help or advise
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Firstly, I would like to ask whether the symptom occurs on an Internal Outlook client or an external Outlook client.
If it occurs on an External Outlook client, I think we are using Outlook Anywhere and we have to add the “mail.abc-company.com” to the domain names in the certificate.
If the error occurs on Internal Outlook, we can workaround this issue by turning off “Outlook Anywhere” by:


1. On a problematic Client, open Outlook.
2. Click Tools >> Account settings.
3. Double click the profile name and click More Settings.
4. On the Connection tab, uncheck on “Connect to Microsoft Exchange using HTTP”.
5. Save the changes and restart the Outlook to check this issue.


No, it did not help.
I am already using RPC connection to Exchange Proxy server and I did settings on  "Connect to Microsoft Exchange using HTTP"
See if there are any steps in this article you may have missed..