В config/environments/production.rb
config.action_mailer.delivery_method = :smtp
config.action_mailer.default_url_options = { host:'your host', port: 'xxx' }
config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true
config.action_mailer.default :charset => "utf-8"
config.action_mailer.smtp_settings = {
:address => "smtp.gmail.com",
:port => 587,
:domain => 'abc.com',
:user_name => "xxxx@mail.com",
:password => "xxxx",
:authentication => :plain,
:enable_starttls_auto => true
}