Telnet port 25 / Telnet SMTP commands / Check
SMTP Port
SMTP
check port 25 with the Telnet command
You
can check your SMTP Server on SMTP port 25 with the following Telnet
commands:
Open a command line and type
telnet
smtp-server.domain.com 25
You can also do
this with PuTTY. Check the "Telnet" radio button and type 25 instead
of 23 in the "Port" textbox.
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 ready at Wed, 20 Mar 2019 20:20:59 +0100
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
Do the following to send an E-Mail from the command line:
220
mailserver.domain.com
Microsoft
ESMTP MAIL Service, Version: 5.0.2195.5329 ready at
Wed, 20 Mar 2019 09:01:29 +0200
helo
myserver.domain.com
# if nothing happens, repeat this
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 Recipient OK
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
In newer Exchange versions
the brackets are obsolete.
If
the mailserver returns a "syntax error" after the
"mail from:" command, you've probably forgotten to put the
mail address in brackets <>.
The
better way to check SMTP port 25
(free command line tool, no installation required)
You can check TCP
port 25 (and other ports) with the
TCP PortCheck command line
tool (www.portcheck-tool.com). It can be used like the Ping
command:
PortCheck.exe MyServer 25
or continuous
PortCheck.exe -t MyServer 25
The result looks like this:
C:\Users\admin>portcheck -t
smtp.office365.com 25
smtp.office365.com - Port 25 - OPEN
- 30ms
smtp.office365.com - Port 25 - OPEN
- 34ms
smtp.office365.com - Port 25 - OPEN
- 40ms
smtp.office365.com - Port 25 - OPEN
- 50ms
smtp.office365.com - Port 25 - OPEN
- 47ms
smtp.office365.com - Port 25 - OPEN
- 30ms
smtp.office365.com - Port 25 -
closed
smtp.office365.com - Port 25 -
closed
smtp.office365.com - Port 25 -
closed
smtp.office365.com - Port 25 -
closed
smtp.office365.com - Port 25 -
closed
smtp.office365.com - Port 25 - OPEN
- 30ms
smtp.office365.com - Port 25 - OPEN
- 29ms
smtp.office365.com - Port 25 - OPEN
- 41ms
smtp.office365.com - Port 25 - OPEN
- 33ms
smtp.office365.com - Port 25 - OPEN
- 30ms
smtp.office365.com - Port 25 - OPEN
- 32ms
smtp.office365.com - Port 25 - OPEN
- 30ms
smtp.office365.com - Port 25 - OPEN
- 34ms
smtp.office365.com - Port 25 - OPEN
- 30ms
smtp.office365.com - Port 25 - OPEN
- 30ms |
The Portcheck tool is also
part of the PingTool software, which is also free. A
ping tool with
TCP portcheck, but also a Wake On
Lan tool (Windows 11).
Another way to check port 25
(free tool)
If
you would like to check your SMTP Server at regular intervals, you
can use the command line tool SLCheck. SLCheck connects to the
SMTP Server and checks the answer. Batch files can be executed in
dependance of the result, e.g. to send alarm notifications. Try the
following command:
SLCheck
-p 25 -a your-server.com -r "220"
220
is the normal answer from a SMTP Server.
All results are logged in a logfile. You can monitor your SMTP
Server by running SLCheck as a scheduled task, e.g. once a minute.
SLCheck Homepage
Content:
Description of telnet smtp commands / How to telnet port 25 / Check
SMTP Port
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