I try to setup ActionMailer with NTLM. I use this gem https://github.com/macks/ruby-ntlm and this example Ruby/Rails ActionMailer not working with NTLM.

My configuration is:

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
   :address => "smtp",
   :port => 587, 
   :domain => "myserver.com",
   :user_name => "[email protected]", 
   :password => "**REMOVED**", 
   :authentication => :ntlm,
   :enable_starttls_auto => false
}

I obtain error from action mailer.

ActionMailer::Base#mail: processed outbound mail in 95.2ms
(irb):7:in `<main>': wrong authentication type ntlm (ArgumentError)