Add support for starting up with a automatically selected available port

[sparsick]

Like Wiremock, Mockserver and Testcontainer are doing it, it would be awesome, if Greenmail could find a free port on the machine by itself. The benefit is that the developer needn't care if the needed port for Greenmail is free on the machine that running the tests.

Furthermore, the developer should have a possibility to ask Greenmail which port is selected.

Current workaround:

    private static int smtpPort = SocketUtils.findAvailableTcpPort();
    private static final ServerSetup SERVER_SETUP_SMTP = new ServerSetup(smtpPort, null, ServerSetup.PROTOCOL_SMTP);

[marcelmay]

If you set the port to 0, GreenMail will actually try to find an available port (see example).

The documentation definitely needs an update describing this feature, and a convenience method for creating a ServerSetup configuration, eg ServerSetup.PROTOCOL_SMTP. dynamicPort() , similar as you suggested with WireMock. Thx alot!

[marcelmay]

Updated example link with dynamicPort()

[sparsick]

Thank you for pointing me to the example and updating the documentation. I didn't find it.