use sendgrid to send emails

config/environments/production.rb

@@ -63,7 +63,6 @@
   # Ignore bad email addresses and do not raise email delivery errors.
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.
   # config.action_mailer.raise_delivery_errors = false
-  config.action_mailer.delivery_method = :sendmail
   config.action_mailer.default_url_options = { host: Gemcutter::HOST,
                                                protocol: Gemcutter::PROTOCOL }
 

config/environments/staging.rb

@@ -63,7 +63,6 @@
   # Ignore bad email addresses and do not raise email delivery errors.
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.
   # config.action_mailer.raise_delivery_errors = false
-  config.action_mailer.delivery_method = :sendmail
   config.action_mailer.default_url_options = { host: Gemcutter::HOST,
                                                protocol: Gemcutter::PROTOCOL }
 

config/initializers/clearance.rb

@@ -1,6 +1,6 @@
 Clearance.configure do |config|
   config.allow_sign_up = (ENV['DISABLE_SIGNUP'].to_s == 'true') ? false : true
-  config.mailer_sender = "help@rubygems.org"
+  config.mailer_sender = "RubyGems.org <no-reply@mailer.rubygems.org>"
   config.secure_cookie = true unless Rails.env.test? || Rails.env.development?
   config.password_strategy = Clearance::PasswordStrategies::BCryptMigrationFromSHA1
 end

config/initializers/sendgrid.rb

@@ -0,0 +1,12 @@
+if Rails.env.production? || Rails.env.staging?
+  ActionMailer::Base.smtp_settings = {
+    address:              'smtp.sendgrid.net',
+    port:                 587,
+    user_name:            ENV['SENDGRID_USERNAME'],
+    password:             ENV['SENDGRID_PASSWORD'],
+    domain:               'mailer.rubygems.org',
+    authentication:       :plain,
+    enable_starttls_auto: true
+  }
+  ActionMailer::Base.delivery_method = :smtp
+end