SMTP check Port 25 with Telnet (Windows)

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TCP Port Check SMTP 25 | 02-Mar-2025

How to check the TCP port 25 (SMTP)

SMTP Check Port 25 with Telnet command

Open a command prompt and enter the following:

telnet smtp-server.domain.com 25

If a functioning mail server can be reached at the address, it will report back something like the following:

220 wp246.webpack.hosteurope.de ESMTP Host Europe Mail Service Wed, 08 Jan 2025 12:06:01 +0100

If the Telnet client is missing on your computer, you must first install this feature. Alternatively, you can also use Putty (link: Putty SMTP Check 25) or the PortCheck tool.

SMTP-Check Port 25 with the PortCheck command

Enter the following in the free command line tool PortCheck:

portcheck.exe <my mailserver> 25

Example:
portcheck.exe EXCH-SRV1 25

Inquires whether the Exchange server EXCH-SRV1 is responding on port 25.

The results are displayed in color (green/red):

Port 25 is the standard mail server port. SMTP is the Simple Mail Transfer Protocol. Most mail servers respond on this port. The encrypted (SSL) SMTP protocol is located on port 465.

To run the check permanently (syntax as for the ping command), use

portcheck.exe -t EXCH-SRV1 25

PortCheck is a portable tool - so no installation is required. The tool can be downloaded from Heise, for example: TCP Portcheck Heise. The PortCheck tool is also part of the PingTool. PingTool 4.3 is able to check TCP ports in a GUI or via command line.

Often used mail TCP ports:

25 - SMTP (Simple Mail Transfer Protocol)

110 - POP3 (Postoffice Protocol)

143 - IMAP4 (Internet Messaging Access Protocol)

587 - SMTP Secure

>>> TCP Ping Homepage

>>> How to find open TCP ports in Windows 11 or Windows Server

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Software: PortCheck
Category: TCP Ping for Windows / Check TCP ports Windows 11
Type: Command line (cmd), TCP port ping, Ping TCP port number
Operating Systems: Windows 7 / Windows 8 / Windows 10 / Windows 11 / Windows Server 2008 / Windows Server 2012 / Windows Server 2016 / Windows Server 2019 / Windows Server 2022