Checking if IMSVA already accepts ECDHE cipher suite

1. Log in to IMSVA command-line interface as root.
2. Execute the command below:

   # openssl s_client -starttls smtp -crlf -connect 127.0.0.1:25 -cipher ECDHE-RSA-AES256-GCM-SHA384

   

   ^{Click the image to enlarge.}

3. Look for the following lines, which means that "ECDHE-RSA-AES256-GCM-SHA384" is not supported.

   New, (NONE), Cipher is (NONE)
   Secure Renegotioation is NOT supported
   

Configuring IMSVA to support ECDHE ciphers

1. Log in to IMSVA command-line interface as root.
2. Execute the command below:

   # postconf -e "smtpd_tls_eecdh_grade=strong"

3. Reload the Postfix configuration:

   # postfix reload

4. Run the following command to verify if ECDHE cipher is already accepted.

   # openssl s_client -starttls smtp -crlf -connect 127.0.0.1:25 -cipher ECDHE-RSA-AES256-GCM-SHA384

   

   ^{Click the image to enlarge.}