In PHX2 there was a working SMTP server on localhost:25 on all Nexus machines. I am not sure, but I believe it worked after we moved to Openstack as well, but this is not 100%. For sure now it does not work anymore.

Please, investigate its configuration and make sure it is operational again. Nexus should be able to send e-mails to users.

Note: the Nexus configuration is set here: https://repository.jboss.org/nexus/#nexus-config