Here is a useful link that I usually refer to.
Actually, this link is a very bad way of testing, it is missing some parts of the ITU standard for SMTP, and using these instructions will cause some perfectly good, working configurations to appear to fail, in the standard to and from email addresses should be enclosed in <> brackets, although many (but not all) email servers will allow it without the brackets, newer MS Exchange servers require the brackets...
http://www.simplescripts.de/smtp-check-port-25-telnet-command.htmSMTP Check Port 25 with the Telnet Command
You can check your SMTP Server on SMTP port 25 with the following Telnet command:
Open a command line and type
telnet smtp-server.domain.com 25
If your server is online a connection will be established on port 25 (SMTP).
An Exchange Server answers with the following output:
220 mailserver.domain.com Microsoft ESMTP MAIL Service, Version: 5.0.2195.5329 ready at Sat, 22 May 2006 08:34:14 +0200
When you type the ‘help’ command the available commands are listed:
214-This server supports the following commands:
214 HELO EHLO STARTTLS RCPT DATA RSET MAIL QUIT HELP AUTH TURN ATRN ETRN BDAT VRFY
Try the following to send an eMail from the command line:
220 mailserver.domain.com Microsoft ESMTP MAIL Service, Version: 5.0.2195.5329 ready at Sat, 22 May 2006 09:01:29 +0200
helo myserver.domain.com
250 mailserver.domain.com Hello [10.1.11.133]
mail from:<myname@mydomain.com>
250 2.1.0 myname@mydomain.com....Sender OK
rcpt to:<recipientname@mydomain.com>
250 2.1.5 recipientname@mydomain.com
data
354 Start mail input; end with <CRLF>.<CRLF>
subject: This is a test mail
to: recipientname@mydomain.com
This is the text of my test mail.
.
250 2.6.0 <exchange.domain.com> Queued mail for delivery
quit
If the mailserver returns a "syntax error" after the "mail from:" command, you've probably forgotten to put the mail address in brackets <>.
There are also several free tools you can use to test SMTP from a Windows PC, here are a few:
http://www.simplecomtools.com/productcart/pc/viewPrd.asp?idproduct=5&idcategory=5http://download.cnet.com/SMTP-Test/3000-2383_4-10592177.htmlhttp://www.softpedia.com/get/PORTABLE-SOFTWARE/Internet/Servers/Portable-SMTP-Tester.shtml