send_grid_test_mail.rb

require 'mail'
Mail.defaults do
  delivery_method :smtp, { :address   => "smtp.sendgrid.net",
                           :port      => 587,
                           :domain    => "xyz.com",
                           :user_name => "xyz@zyz.com",
                           :password  => "xyz",
                           :authentication => 'plain',
                           :enable_starttls_auto => true }
end

mail = Mail.deliver do
  to 'vivek@weboniselab.com'
  from 'vivek@weboniselab.com'
  subject 'This is the subject of your email'
  text_part do
    body 'Hello world in text'
  end
  html_part do
    content_type 'text/html; charset=UTF-8'
    body '<b>Hello world in HTML</b>'
  end
end