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I have a quick question about tcpdump. I'm having an issue with a particular email client not being able to start a STARTTLS connection with my email server. I want to view the entire connection using tcpdump. I tried using the following command to write it to a file:
tcpdump -i eth1 dst port 25 -w <temporary filename>
When displaying the results of the temporary file, it was mostly gibberish. I could see the EHLO command and the QUIT command, but that was about it. How should I be viewing this such that it makes sense? Or do I have the tcpdump command wrong?
What I'm looking for specifically is to see that the STARTTLS command is being sent by the user's client. I can't see it amongst the gibberish, but that doesn't mean it's not there. I will try the command you suggested.
I was also asking just for my own personal information. I foresee myself troubleshooting an FTP issue in the future as well, which, of course, won't be encrypted.
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