How to renew expiring Exchange Server 2007 Internal Transport Certificate

Administrators of the Exchange Server 2007 (especially the ones who regularly check their event logs) might, sooner or later, come across warnings about the expiring Internal Transport Certificate – it will be highlighted with messages like these:

The STARTTLS certificate will expire soon.

or

An internal transport certificate will expire soon.

Those that don’t check their logs will probably be reminded by their users to do so – when nearing a certificate expiry, users’ Outlooks will start displaying messages saying:

[domain name]
Information you exchange with this site cannot be viewed or changed by others.
However, there is problem with the site's security certificate…

Exchange Server 2007 Internal Transport Certificate is an important part of the system (for example allowing the users to access OWA through a safe HTTPS protocol) but it is often overlooked by some administrators, especially the ones who worked with previous versions of Exchange and simply were not aware of the existence of such a feature. Fortunately, renewing a certificate that nears its expiration date is relatively easy and can be achieved following the steps described below.

Check the currently installed certificate.

Open the Exchange Management Shell and there type get-exchangecertificate | List (Fig. 1).

Fig.1. Exchange Certificate details.

You should see detailed information about your current certificate. The following values are the ones you need to pay the most attention to:

NotAfter – this is a very important thing, it shows the final expiry date of your certificate.
Services – shows the services the certificate applies to.
Thumbprint – this is a very important value as well, since it is the identification of the certificate and it is necessary to make any changes to it.

Create a new certificate.

In the Exchange Management Shell window, run the following command: new-exchangecertificate - you will get a warning message asking whether you are sure you want to overwrite your old certificate (Fig. 2.).

Fig.2. Overwriting the old certificate.

Once you agree to make the changes run the get-exchangecertificate | List command again. This is what you should see:

Fig.3. New and old certificate details.

Activate the new certificate.

As you can see from the above screenshot, the IIS service is still using the old certificate. In order to fix this, you will have to enable the new one using the enable-exchangecertificate command. And to do this, you will need the certificate thumbnail value I mentioned before.  So the whole command you should use will be:

enable-exchangecertificate -Thumbprint [YOUR NEW CERTIFICATE THUMBRINT VALUE]

You will also need to provide the name of the service that needs to be included in the new certificate (in this case it is IIS).

Fig.4. Assigning the IIS service to the new certificate.

 Remove the old certificate.

Now you can safely remove the old certificate, which is no longer necessary. Type:

remove-exchangecertificate -Thumbprint [YOUR OLD CERTIFICATE THUMBRINT VALUE]

Once you’re done, run the get-exchangecertificate | List command for the last time. This should be your final result:

Fig.5. New Exchange Certificate active and running.

As you can see, the certificate is valid, all services are included and there is still a long time before it expires again. I hope this tutorial will help everyone who needs help with their expiring Exchange Certificate. Good luck!