SMTP Check Port 25 with the Telnet Command
You can check your SMTP Server on SMTP port 25 with the following Telnet command. Note that these instructions are for the Windows OS platform. For Macintosh, please google "mac telnet port 25"
Open a command line and type the following, using your actual domain where is says 'mailserver.domain.com'
Note that if your computer does not support telnet, open the Programs and Features Control Panel applet (Start, Control Panel, Programs and Features). Select "Turn Windows features on or off." Select the Telnet Client option and click OK. A dialog box appears, confirming the installation of new features. After installation is complete, close the main Programs and Features Control Panel applet. The telnet command should now be available.
telnet mailserver.domain.com 25
If your server is online a connection will be established on port 25 (SMTP). If you cannot connect then your IPS or local firewall is blocking port 25. You can try to use port 26 or 587 in your email setup instead.
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
250 mailserver.domain.com Hello [10.1.11.133]
250 2.1.0 email@example.com....Sender OK
250 2.1.5 firstname.lastname@example.org
354 Start mail input; end with <CRLF>.<CRLF>
subject: This is a test mail
This is the text of my test mail.
250 2.6.0 <exchange.domain.com> Queued mail for delivery