Running JRuby in NetBeans: ------------------------- require 'rubygems' require 'mailfactory' mail = MailFactory.new() mail.to = 'to address' mail.from = 'from address' mail.subject = 'subject' mail.text = 'message' puts mail.to_s --returns nil Running JIRB: ------------ jirb> require 'rubygems' jirb> require 'mailfactory' jirb> mail = MailFactory.new() jirb> mail.to_s NoMethodError: undefined or inaccessible method `euid' for Process:Module from C:/jruby-1.0.0RC2/lib/ruby/gems/1.8/gems/mailfactory-1.2.3/lib/mail factory.rb:181:in `method_missing' from C:/jruby-1.0.0RC2/lib/ruby/gems/1.8/gems/mailfactory-1.2.3/lib/mail factory.rb:181:in `construct' from C:/jruby-1.0.0RC2/lib/ruby/gems/1.8/gems/mailfactory-1.2.3/lib/mail factory.rb:211:in `to_s' from (irb):1:in `binding' irb(main):011:0> Although reported on line 181, the error appears to stem from line 182 of factory.rb: add_header("Message-ID", "<#{Time.now.to_f()}.#{Process.euid()}.#{String.new.object_id()}@#{sendingdomain}>") ^^^^^^^^^^^^^^ According to the API docs: Process.euid => fixnum Returns the effective user ID for this process. Process.euid #=> 501