Office 365 - Exchange Error

whorsfall used Ask the Experts™

I am using an Apple Mac - with Outlook 2016 and getting the following error when I log into Outlook.

Verify Certificate

A secure connection cannot be established with the server xxxx.xx.xx because its intermediate or root certificate cannot be found.
Do you want to continue.

If you continue, the information that you view and send will be encrypted, but will not be secure.

There is an option to always trust. But this does not seem the best way of fix it.

So how can I resolve this issue so the dialog does not appear.


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You may have expired Certs in the keychain that need to be cleared out and updated.

see the following link:

all the best



Thanks for the info. I did configure the email with the automatic options - and it did then connect to exchange. So should I be overriding these settings?

I have attached the specific error - as the article you said talks about a different certificate to the one I am getting.

Maybee I am misunderstanding the steps.


Is it an On Premise Exchange Server?

I had this issue and it was the certificate i had installed in Exchange 2013.

I have an Exchange Server and an RDS Server and they had separate certificates and the common name on the Exchange server cert was which was the URL exchange was looking to for al its services and a separate cert for for the RDS server.

I found that when i used a UCC SAN cert for the RDS server with common name and the SAN's as and installed it on the RDS server through IIS, exported and imported it on the Exchange server all was good.

Not sure what would be better, changing Exchange or get a new certificate.

Not sure if this is your scenario but hope it helps..

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