We should use the same pattern than NXP-26563 to try to bind to different port in case `2525` is not available.
See `org.nuxeo.ecm.core.test.FakeSmtpMailServerFeature` and `org.nuxeo.runtime.test.runner.ServletContainerFeature#findFreePort`
Aslo doing some cleanup around FT that are relying in FakeSmtpServer feature which were used only as a workaround to have a workable Smtp server, but any test is checking mail content and behavior of FakeSmtp is to change mail.properties file which is actually not read at all.