Exchange / Outlook – Security Alert – “The security certificate was issued by a company you have not chosen to trust”

KB ID 0000454


Out of the box Exchange 2007 and 2010 comes with a “Self Signed” digital certificate. That’s OK for getting you up and running but your Outlook clients may start to see the error below.

The security certificate was issued by a company you have no chosen to trust

Security Alert
Information you exchange with this site cannot be viewed or changed by others. However, there is a problem with the sites security certificate.
The security certificate was issued by a company you have chosen not to trust. View the Certificate to determine whether you want to trust the certifying authority.


You have a number of options to stop this error.

Option 1 (This is WHAT YOU SHOULD DO!)

You should purchase a certificate signed by a trusted certification authority, these used to cost a fortune, but if you shop around you can pick them up very cheaply.

Obtaining, and Installing an Exchange Certificate.

Option 2 (Free, and handy if you don’t have a lot of clients)

It still amazes me that people with pay out for a new server, and Exchange, but then refuse to buy a certificate? But if your reading this then that might well be you. You can choose to trust the certificate that’s being presented to you. You carry out this procedure on each Outlook client. If you have a lot of Outlook clients then skip to options 3 and 4).

1. First, start up Outlook and get the error message on the screen.

Import exchange cert

2. Select “View Certificate” > Install Certificate > Next.

Outlook install certificate

3.Selct “Place all certificates in the following store” > Browse > Select “Trusted Root Certification Authority > OK.

Outlook add certificate

4. Finish.

Outlook trust certificate

5. Select yes to accept the certificate import> Restart Outlook.

Outlook import cert

Option 3 (Free, and handy if you have a lot of clients)

Install Certificates with Group Policy GPO

Option 4

Install your own certification authority, and sign your own Exchange certificate. Great if you already have a CA, though it’s a mess about just to solve this problem.


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Author: Migrated

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