Do you have an application which needs a smtp server but you don't really care about sending email through it? Are you developing a new application in kubernetes and do you need a smtp microservice to debug sending mails?
This is a simple python DebuggingServer from smtplib that allows you to provide a smtp server which always accepts mails and print them to stdout or not (see Privacy)
You can find an example here
By default this container logs all the incoming emails in stdout for debugging
purpose, if you prefer to avoid this behavior just set the env var NOLOG to value 1.