HTTP listens on port 80. Can therefore issue command telnet hostname 80 , to connect to HTTP. Can then issue GET /index.html
If the file exists and everything is OK, contents of file will appear on screen, otherwise an error message will appear.
SMTP listens on port 25. Enter command telnet hostname 25 and start a short conversation,e.g.
MAIL FROM:hotmail.com> RCPT TO:email@example.com
If OK, SMTP will respond to conversation. Can type quit to end conversation.
To send actual mail using SMTP commands, do the following:
1. telnet hostname port_number 2. HELO domainname 3. MAIL FROM: email_address 4. RCPT TO: email_address 5. DATA 6. type in message 7. . 8. mail has been sent, enter QUIT to exit