What is DevNull SMTP

It is a dummy SMTP server that can be used for testing purposes. It helps you see all communication between a client and the server and is very useful if you are trying to find problems with your email server or a client that you wrote.

Consider the following scenarios.
1 Assume you are having problems with your email server. You can try sending an email to:
This is assuming that the IP address of your machine is Your email server will send a message back to your machine and you will be able to see if it works.
2 Lets say you are writing an application that needs to send emails. Rather then sending it to actual recipients you can configure your application to send it to the DevNull server.


You need Java (JDK 1.4 or newer) installed on your machine before you can run it.

Where do emails go?

Nowhere - hence the name "DevNull". Every email that is sent to this server gets deleted. The purpose of this application is to debug and test other applications that need to send emails.

Note that this SMTP server only supports minimal SMTP commands specified by RFC 821


You can either download DevNullSMTP or run it as an Applet within your browser.
Download Run as Applet
Click here to download. Once downloaded run the application by typing the following command.

You only need this one file to run the application. Click here for additional usage instructions

    java -jar DevNullSmtp.jar

Typically SMTP servers listen on TCP/IP port 25, which is a privileged port and Java applets are not allowed to open a TCP/IP socket on this port. In order to bypass this restriction we had to sign the JAR files. If you decide to chose this option you will have to accept our signed certificate on the next page.

Click here to run it as an applet.

Run as Applet

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