Rails 3 - Production environment - smtp email issue

I am using smtp settings for sending mails in rails 3. It works fine when sendmail and postfix services are running. But when I stopped those two services then mails stop stop sending and giving me connection error.

Error log -

ERROR -- : (Errno::ECONNREFUSED): Connection refused - Connection refused
org/jruby/ext/socket/RubyTCPSocket.java:126:in `initialize'
org/jruby/RubyIO.java:1178:in `open'