Net::SMTPAuthenticationError for sending mail through rails action mailer

I am using rails action mailer but got this error "Net::SMTPAuthenticationError".I also enable the Less Secure apps but still got this error.

config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true
config.action_mailer.delivery_method = :smtp
    ActionMailer::Base.smtp_settings = {
    :user_name => "my_email",
    :password => "password",
    :domain => 'gmail.com',
    :address => 'smtp.gmail.com',
    :port => 587,
    :authentication => :plain 
    }