For the purpose of troubleshooting, I need to see what an email looks like when it's sent to my sendmail server via SMTP. The upstream server requires the SMTP connection to use STARTTLS so a packet capture only shows me encrypted data.
Is there a way to use wireshark to decrypt the transmission and see? Assuming of course that I have the private key used on my sendmail server?
I see several procedures available online referencing the
RSA key lists feature in wireshark (for example: https://support.citrix.com/article/CTX116557). But this still doesn't seem to be working for me.
Is this related to forward secrecy? Can I just not do this on newer protocols / ciphers?