Skip to content

Testing KumoMTA

Now that you have KumoMTA installed, you should test it from the command line of the installed host. This is easy if you installed the basic tools as described earlier.

Note that the default SMTP listener is on port 25, so we have use that in these examples.

Telnet method for SMTP

Start a telnet session with telnet localhost 25, replacing with your actual email address:

ehlo moto
subject: My First Email

Hey, this is my first email!


If you have not specifically requested outbound use of port 25 from AWS, then it is very possible the message will not be delivered.

Curl method for HTTP API

$ curl -H 'Content-Type: application/json' '' -d '{
    "envelope_sender": "",
    "content": "Subject: hello\n\nHello there",
    "recipients": [
            "email": ""

See the HTTP injection API reference for more information.

Using Swaks for testing

Swaks, the Swiss Army Knife for SMTP by John Jetmore is a fantastic tool for testing.

Install Swaks:

curl -O
tar -xvzf swaks-20201014.0.tar.gz
chmod 755 ./swaks-20201014.0/swaks

Basic Swaks usage:

swaks --to --server --port 25

Regardless of testing method used, the next step is to check the logs.