Actually your local ISP won't see your port 25 request. For example, one of my domains is basicmail.net and I would like to use smtp.basicmail.net on port 25 on basicmail.net to send mail. If I had access to a standard shell on basicmail.net (I'm not sure about a jailshell) I could log in and send mail OR I could set up a secure shell from my local machine to basicmail.net and when ever I tried to send mail on a port 25 it would get forwarded over the ssh link and send on the remote host - basicmail.net in this case. The local ISP would only see an encrypted connect from my machine to the remote machine on a SSH port, they wouldn't otherwise have any access to it.
For example, if JailShell would work, here is a command that would do the trick replacing SMTPSERVER, USERNAME, and REMOTEHOST with the correct values:
ssh -L 25:SMTPSERVER:25 -L -l USERNAME REMOTEHOST
Then, anytime you sent something on port 25, it would pop out at REMOTEHOST and would get there via a SSH port which isn't port 25.
I guess the question I have is can one log into a JailShell and sent mail on port 25? If so, then I should be able to build an encrypted pipe using SSH to get there and have mail go down that pipe and pop out at the desired smtp server bypassing the ISP entirely!
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dudescholar