Securing a Exchange 2007 Client Access server, with a signed certificates

First to request a certificates start Exchange Management Shell

Type this into the console:

New-ExchangeCertificate -DomainName exchange01.domainname.local, webmail.domain.prefix -FriendlyName ”Microsoft Exchange” -GenerateRequest:$True -Keysize 2048 -path c:\certrequest.txt -privatekeyExportable:$true -subjectName “c=DK, o=organization name, CN=webmail.domain.prefix”

Change domainname.local, domain.prefix (2 places) and last change you organization name.

Now you get a file, name c:\certrequest.txt. The content of this file, you can send this to yours 3rd party certificate authority.
After this you got an a signed certificates back, as you need to import into the Exchange servers, this is done like this.

Copy the sign certificates to a file in the root of c:\ name signcert.txt
And run this in the Exchange console

Import-ExchangeCertificate –Path c:\signcert.txt | Enable-ExchangeCertificate –Services IIS,POP,IMAP,SMTP