We have a Win2k3 server with IIS6 SMTP installed and configured. We only need inbound mail for this, which is working fine at the moment for testing, but there's no encryption configured at this time. When it goes to production, the sending servers from the Net will all use TLS to encrypt the traffic.

We do have a wildcard cert from a 3rd party for *.domain.com but I can't seem to import it into the SMTP properties. I have imported the crt file onto the server, but nothing shows up when I go through the IIS Certificate Wizard.

Is there something else I can try or do I need a new cert? If so, can I use one from an internal CA or would it need to be from a 3rd party?


.crt files usually contain an X.509 certificate, which has only the public key. IIS needs both the certificate and private key to act as a TLS server.

Often, you can export the cert and the private key together in PKCS#12 format (.pfx/.p12).

If you have the private key in a separate .key or .pem file, you should be able to use OpenSSL to combine them:

openssl pkcs12 -export -in foo.crt -inkey foo.key -out foo.p12

(Sometimes -inform der is necessary.)

  • grawity, thanks for the response. Shortly after I posted the question, I got assistance from a colleague who recommended that I export the cert from a working server then import it into IIS on this server. This allowed me to attach it to the SMTP virtual server without any further issues. Thanks again! – Agent Feb 16 '11 at 18:51

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