Send emails through zimbra using "windows" command prompt

You cannot do it "without any third party software" but with zimbra, because your zimbra is already third party. :-)

First of all, don't use "command prompt" (CMD.EXE). Using it is a common mistake. Use just the file name of the application you want to start and, second parameter, it's command line. Please see:
http://msdn.microsoft.com/en-us/library/system.diagnostics.process.start.aspx[^].

If you really want it without third party, you should do it without third party. For example, you can use this:
http://msdn.microsoft.com/en-us/library/system.net.mail.smtpclient.aspx[^].

In all cases, you will need some service serving as an entry point into the main system. It could be SMTP server, some Web service or mail Web site, etc.

—SA

Zimbra should expose and SMTP port that you can authenticate to and then send emails via. Check out their link on outgoing smtp settings[^] to see how to get it configured.

In terms of sending an email from the command line, if your system has powershell installed you can just run a simple script. Check out sending emails from the windows command line to see what script to run, and then just plug in your server details, credentials, message subject, body, to and from address and you should be done.