Telnet - How can I use telnet to test a web or mail server?

How can I use telnet to test a web or mail server?

Telnet applications are useful for testing remote services such as web services or smtp mail servers. You just need to telnet to the appropriate ip and port, and know how to issue commands for the relevant protocol such as HTTP or SMTP.

As an example, you can use telnet to request a web page from a remote server with just a couple of commands:

• $ telnet example.com 80
• GET /path/to/page.htm

Here's an example for telneting to google.com and requesting the index page:

[rain ~]$telnet google.com 80
    Trying 74.125.225.224...
    Connected to google.com.
    Escape character is '^]'.
    GET /
    HTTP/1.0 200 OK
    Date: Mon, 30 Sep 2013 02:21:47 GMT
    Expires: -1
    Cache-Control: private, max-age=0
    Content-Type: text/html; charset=ISO-8859-1
    
    --snip-remaining-output--
    
    Connection closed by foreign host.