sendgrid.rb

require 'sendgrid-ruby'

client = SendGrid::Client.new(api_key: 'XXXXXXXXXXXXXXXXXXXXX')

res = client.send(SendGrid::Mail.new(to: 'XXXXXXXX@XXXX.XXX', from: 'test@example.com', subject: 'Hello world!', text: 'Hi there!', html: '<b>Hi there!</b>'))
puts res.code
puts res.body