SMTP HTTP HTTP CONNECT HTTP proxy # # Server-side HTTP/1.1 200 Mighty fine indeed smtp: sure hit me # # Client-side smtp http-proxy http proxy SMTP send tunneled through HTTP proxy From: different To: another body smtp://smtp.1320:%SMTPPORT/1320 --mail-rcpt recipient@example.com --mail-from sender@example.com -T - -p -x %HOSTIP:%PROXYPORT # # Verify data after the test has been "shot" EHLO 1320 MAIL FROM: RCPT TO: DATA QUIT From: different To: another body . CONNECT smtp.1320:%SMTPPORT HTTP/1.1 Host: smtp.1320:%SMTPPORT User-Agent: curl/%VERSION Proxy-Connection: Keep-Alive