In order to have a proof for having sent a mail from my computer, how to send IP address of my machine also along with mail?
This feature is already there in most of the web mail services today. If you check the headers of a message, you can find sender’s IP Address or the sending SMTP server’s IP Address. Also nowadays, if you send e-mails from yahoo or hotmail or mail4india you may find a header X-Originator: IP Address or Received from: IP Address to find the IP address of the sender. If sender is behind the proxy/firewall, it shows the IP Address of the proxy server/firewall.