It appears that ISPconfig created an alias that rewrites email@example.com to
firstname.lastname@example.org, but I think it should be "email@example.com". Is there a place in ISPConfig to fix this.. or do have to fix the alias individually?
There is nothing wrong with that, its the intended behaviour. Make sure that ubuntu.elatia.net is set in DNS or the local hosts file to point to your server.