Setting ActionMailer

development.rb

config.action_mailer.default_url_options = { :host => '172.16.77.88:3000' }
#remmembe to set in production.rb ,also

devise.rb

config.mailer_sender = "[email protected]"

migration

# rails g migration add_confirmable_to_devise
class AddConfirmableToDevise < ActiveRecord::Migration
  def self.up
    add_column :users, :confirmation_token, :string
    add_column :users, :confirmed_at,       :datetime
    add_column :users, :confirmation_sent_at , :datetime
    add_column :users, :unconfirmed_email, :string

    add_index  :users, :confirmation_token, :unique => true
  end
  def self.down
    remove_index  :users, :confirmation_token

    remove_column :users, :unconfirmed_email
    remove_column :users, :confirmation_sent_at
    remove_column :users, :confirmed_at
    remove_column :users, :confirmation_token
  end
end

user_mailer.rb

  def confirm(email)
    @greeting = "Hi"
    @message = "Thank you for confirmation!"
    mail to: email
  end