postfix debian etch security certificate can't be virified

I did the http://www.howtoforge.com/virtual_users_and_domains_with_postfix_debian_etch
and when I start Outlook Express, I get

" The server you are connected to is using a security certificate that could not be verifies. A certificate chain processed, but terminated in a root certificate which is not trusted by the trust pprovider. Do you want to continue using this server ? "

When I click on yes everything works but can I install the certificate so I am not asked this question every time I start Outlook ?

 

What Common Name did you enter when you created the cert? Was it your hostname?

 

Code:

cat /etc/courier/pop3d.pem

Copy data between "-----BEGIN CERTIFICATE-----" and "-----END CERTIFICATE-----". Create a new text file in your Windows desktop and paste this information. Then, rename new text file to .crt.

I don't have english version of Windows, so I don't know exactily steps.
Double click on .crt file. Click on Install certificate... next... put all certificates in store... find... choose Root certificate... ok... next... finish.
You will be prompted to install new certificate and it's done ^^