title: rails s gets error for devise configuration to send mail
body: <p>config/initializers/devise.rb=></p>
  
  <pre><code># Use this hook to configure devise mailer, warden hooks and so forth. The first
  # four configuration values can also be set straight in your models.
  Devise.setup do |config|
    # ==&gt; Mailer Configuration
    # Configure the e-mail address which will be shown in Devise::Mailer,
    # note that it will be overwritten if you use your own mailer class with default "from" parameter.
    config.mailer_sender = "abc@gmail.com"
  
    # Configure the class responsible to send e-mails.
     config.mailer = "Devise::Mailer"
  
    # ==&gt; ORM configuration
    # Load and configure the ORM. Supports :active_record (default) and
    # :mongoid (bson_ext recommended) by default. Other ORMs may be
    # available as additional gems.
    require 'devise/orm/active_record'
  
    # ==&gt; Configuration for any authentication mechanism
    # Configure which keys are used when authenticating a user. The default is
    # just :email. You can configure it to use [:username, :subdomain], so for
    # authenticating a user, both parameters are required. Remember that those
    # parameters are used only when authenticating and not when retrieving from
    # session. If you need permissions, you should implement that in a before filter.
    # You can also supply a hash where the value is a boolean determining whether
    # or not authentication should be aborted when the value is not present.
    # config.authentication_keys = [ :email ]
  
    # Configure parameters from the request object used for authentication. Each entry
    # given should be a request method and it will automatically be passed to the
    # find_for_authentication method and considered in your model lookup. For instance,
    # if you set :request_keys to [:subdomain], :subdomain will be used on authentication.
    # The same considerations mentioned for authentication_keys also apply to request_keys.
    # config.request_keys = []
  
    # Configure which authentication keys should be case-insensitive.
    # These keys will be downcased upon creating or modifying a user and when used
    # to authenticate or find a user. Default is :email.
    config.case_insensitive_keys = [ :email ]
  
    # Configure which authentication keys should have whitespace stripped.
    # These keys will have whitespace before and after removed upon creating or
    # modifying a user and when used to authenticate or find a user. Default is :email.
    config.strip_whitespace_keys = [ :email ]
  
    # Tell if authentication through request.params is enabled. True by default.
    # config.params_authenticatable = true
  
    # Tell if authentication through HTTP Basic Auth is enabled. False by default.
    # config.http_authenticatable = false
  
    # If http headers should be returned for AJAX requests. True by default.
    # config.http_authenticatable_on_xhr = true
  
    # The realm used in Http Basic Authentication. "Application" by default.
    # config.http_authentication_realm = "Application"
  
    # It will change confirmation, password recovery and other workflows
    # to behave the same regardless if the e-mail provided was right or wrong.
    # Does not affect registerable.
    # config.paranoid = true
  
    # ==&gt; Configuration for :database_authenticatable
    # For bcrypt, this is the cost for hashing the password and defaults to 10. If
    # using other encryptors, it sets how many times you want the password re-encrypted.
    #
    # Limiting the stretches to just one in testing will increase the performance of
    # your test suite dramatically. However, it is STRONGLY RECOMMENDED to not use
    # a value less than 10 in other environments.
    config.stretches = Rails.env.test? ? 1 : 10
  
    # Setup a pepper to generate the encrypted password.
    # config.pepper = "b1179d3eccc2985aa7e9e438d8866464943f84449e53014c19852e795fdc4c17ca0b779e843ea8826589c213aff8c91c16c4a937685a183b622899e0dbf120a6"
  
    # ==&gt; Configuration for :confirmable
    # A period that the user is allowed to access the website even without
    # confirming his account. For instance, if set to 2.days, the user will be
    # able to access the website for two days without confirming his account,
    # access will be blocked just in the third day. Default is 0.days, meaning
    # the user cannot access the website without confirming his account.
    # config.confirm_within = 2.days
  
    # Defines which key will be used when confirming an account
    # config.confirmation_keys = [ :email ]
  
    # ==&gt; Configuration for :rememberable
    # The time the user will be remembered without asking for credentials again.
    # config.remember_for = 2.weeks
  
    # If true, a valid remember token can be re-used between multiple browsers.
    # config.remember_across_browsers = true
  
    # If true, extends the user's remember period when remembered via cookie.
    # config.extend_remember_period = false
  
    # If true, uses the password salt as remember token. This should be turned
    # to false if you are not using database authenticatable.
    config.use_salt_as_remember_token = true
  
    # Options to be passed to the created cookie. For instance, you can set
    # :secure =&gt; true in order to force SSL only cookies.
    # config.cookie_options = {}
  
    # ==&gt; Configuration for :validatable
    # Range for password length. Default is 6..128.
    # config.password_length = 6..128
  
    # Email regex used to validate email formats. It simply asserts that
    # an one (and only one) @ exists in the given string. This is mainly
    # to give user feedback and not to assert the e-mail validity.
    # config.email_regexp = /\A[^@]+@[^@]+\z/
  
    # ==&gt; Configuration for :timeoutable
    # The time you want to timeout the user session without activity. After this
    # time the user will be asked for credentials again. Default is 30 minutes.
    # config.timeout_in = 30.minutes
  
    # ==&gt; Configuration for :lockable
    # Defines which strategy will be used to lock an account.
    # :failed_attempts = Locks an account after a number of failed attempts to sign in.
    # :none            = No lock strategy. You should handle locking by yourself.
    # config.lock_strategy = :failed_attempts
  
    # Defines which key will be used when locking and unlocking an account
    # config.unlock_keys = [ :email ]
  
    # Defines which strategy will be used to unlock an account.
    # :email = Sends an unlock link to the user email
    # :time  = Re-enables login after a certain amount of time (see :unlock_in below)
    # :both  = Enables both strategies
    # :none  = No unlock strategy. You should handle unlocking by yourself.
    # config.unlock_strategy = :both
  
    # Number of authentication tries before locking an account if lock_strategy
    # is failed attempts.
    # config.maximum_attempts = 20
  
    # Time interval to unlock the account if :time is enabled as unlock_strategy.
    # config.unlock_in = 1.hour
  
    # ==&gt; Configuration for :recoverable
    #
    # Defines which key will be used when recovering the password for an account
    # config.reset_password_keys = [ :email ]
  
    # Time interval you can reset your password with a reset password key.
    # Don't put a too small interval or your users won't have the time to
    # change their passwords.
    config.reset_password_within = 2.hours
  
    # ==&gt; Configuration for :encryptable
    # Allow you to use another encryption algorithm besides bcrypt (default). You can use
    # :sha1, :sha512 or encryptors from others authentication tools as :clearance_sha1,
    # :authlogic_sha512 (then you should set stretches above to 20 for default behavior)
    # and :restful_authentication_sha1 (then you should set stretches to 10, and copy
    # REST_AUTH_SITE_KEY to pepper)
    # config.encryptor = :sha512
  
    # ==&gt; Configuration for :token_authenticatable
    # Defines name of the authentication token params key
    # config.token_authentication_key = :auth_token
  
    # If true, authentication through token does not store user in session and needs
    # to be supplied on each request. Useful if you are using the token as API token.
    # config.stateless_token = false
  
    # ==&gt; Scopes configuration
    # Turn scoped views on. Before rendering "sessions/new", it will first check for
    # "users/sessions/new". It's turned off by default because it's slower if you
    # are using only default views.
    # config.scoped_views = false
  
    # Configure the default scope given to Warden. By default it's the first
    # devise role declared in your routes (usually :user).
    # config.default_scope = :user
  
    # Configure sign_out behavior.
    # Sign_out action can be scoped (i.e. /users/sign_out affects only :user scope).
    # The default is true, which means any logout action will sign out all active scopes.
    # config.sign_out_all_scopes = true
  
    # ==&gt; Navigation configuration
    # Lists the formats that should be treated as navigational. Formats like
    # :html, should redirect to the sign in page when the user does not have
    # access, but formats like :xml or :json, should return 401.
    #
    # If you have any extra navigational formats, like :iphone or :mobile, you
    # should add them to the navigational formats lists.
    #
    # The :"*/*" and "*/*" formats below is required to match Internet
    # Explorer requests.
    # config.navigational_formats = [:"*/*", "*/*", :html]
  
    # The default HTTP method used to sign out a resource. Default is :delete.
    config.sign_out_via = :delete
  
    # ==&gt; OmniAuth
    # Add a new OmniAuth provider. Check the wiki for more information on setting
    # up on your models and hooks.
    # config.omniauth :github, 'APP_ID', 'APP_SECRET', :scope =&gt; 'user,public_repo'
  
    # ==&gt; Warden configuration
    # If you want to use other strategies, that are not supported by Devise, or
    # change the failure app, you can configure them inside the config.warden block.
    #
    # config.warden do |manager|
    #   manager.failure_app   = AnotherApp
    #   manager.intercept_401 = false
    #   manager.default_strategies(:scope =&gt; :user).unshift :some_external_strategy
    # end
  
    config.action_mailer.delivery_method = :smtp
  
    config.action_mailer.smtp_settings = {
      :tls =&gt; true,
      :enable_starttls_auto =&gt; true,
      :address =&gt; "smtp.gmail.com",
      :port =&gt; "587",
      :domain =&gt; "gmail.com",
      :authentication =&gt; :plain,
      :user_name =&gt; "abc@gmail.com",
      :password =&gt; "abc"
      }
  
  end
  </code></pre>
  
  <p>If i remove these=></p>
  
  <pre><code>  config.action_mailer.delivery_method = :smtp
  
    config.action_mailer.smtp_settings = {
      :tls =&gt; true,
      :enable_starttls_auto =&gt; true,
      :address =&gt; "smtp.gmail.com",
      :port =&gt; "587",
      :domain =&gt; "gmail.com",
      :authentication =&gt; :plain,
      :user_name =&gt; "abc@gmail.com",
      :password =&gt; "abc"
      }
  </code></pre>
  
  <p>then there is no problem.</p>
  
  <p>Otherwise if i do rails s i get error=></p>
  
  <pre><code>=&gt; Booting WEBrick
  =&gt; Rails 3.1.1 application starting in development on http://0.0.0.0:3000
  =&gt; Call with -d to detach
  =&gt; Ctrl-C to shutdown server
  Exiting
  /home/user1/rorblog/config/initializers/devise.rb:211:in `block in &lt;top (required)&gt;': undefined method `action_mailer' for Devise:Module (NoMethodError)
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/devise-1.4.8/lib/devise.rb:250:in `setup'
      from /home/user1/rorblog/config/initializers/devise.rb:3:in `&lt;top (required)&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:234:in `load'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:234:in `block in load'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:223:in `block in load_dependency'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:640:in `new_constants_in'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:223:in `load_dependency'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:234:in `load'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/engine.rb:556:in `block (2 levels) in &lt;class:Engine&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/engine.rb:555:in `each'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/engine.rb:555:in `block in &lt;class:Engine&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/initializable.rb:30:in `instance_exec'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/initializable.rb:30:in `run'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/initializable.rb:55:in `block in run_initializers'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/initializable.rb:54:in `each'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/initializable.rb:54:in `run_initializers'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/application.rb:96:in `initialize!'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/railtie/configurable.rb:30:in `method_missing'
      from /home/user1/rorblog/config/environment.rb:5:in `&lt;top (required)&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `require'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `block in require'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:223:in `block in load_dependency'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:640:in `new_constants_in'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:223:in `load_dependency'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `require'
      from /home/user1/rorblog/config.ru:4:in `block in &lt;main&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/builder.rb:51:in `instance_eval'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/builder.rb:51:in `initialize'
      from /home/user1/rorblog/config.ru:1:in `new'
      from /home/user1/rorblog/config.ru:1:in `&lt;main&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/builder.rb:40:in `eval'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/builder.rb:40:in `parse_file'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/server.rb:200:in `app'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/commands/server.rb:46:in `app'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/server.rb:301:in `wrapped_app'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.3/lib/rack/server.rb:252:in `start'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/commands/server.rb:70:in `start'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/commands.rb:54:in `block in &lt;top (required)&gt;'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/commands.rb:49:in `tap'
      from /home/user1/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.1.1/lib/rails/commands.rb:49:in `&lt;top (required)&gt;'
      from script/rails:6:in `require'
      from script/rails:6:in `&lt;main&gt;'
  </code></pre>