How to send reply mail to particular mail using mailman server in ruby on rails

I want to send acknowledge mail to a particular mail using mailman server. I tried many times to do that. But I did not get any solutions. Please advise me to do the thing.

This is very simple:

I like to have an initializer for handle this, like so:

config/initializers/setup_email.rb

if Rails.env.production?
 ActionMailer::Base.smtp_settings = {
  :user_name => ENV['SENDGRID_USERNAME'],
  :password => ENV['SENDGRID_PASSWORD'],
  :domain => ENV['SENDGRID_DOMAIN'],
  :address => "smtp.sendgrid.net",
  :port => 587,
  :authentication => :plain,
  :enable_starttls_auto => true
 }
end

And then for the production and development environments you have to do something like so:

config/environments/production.rb

config.action_mailer.default_url_options = { host: "http://www.example.com" }
config.action_mailer.asset_host = "http://www.example.com"

As for the development environment I recommend you install the mailcatcher gem:

$ gem install mailcatcher

Once is installed, run the mailcatcher command:

$ mailcatcher

This will enable a web page on http://127.0.0.1:1080 to where every email will be send and you'll be able to preview them. Just make sure your have the following configuration

config/environments/development.rb

config.action_mailer.default_url_options = { host: "localhost:3000" }
config.action_mailer.asset_host = "http://localhost:3000"

#mailcatcher configs
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = { :address => "localhost", :port => 1025 }

Then you should be fine!