Post SMTP Compatibility & Integrations Post SMTP integrations allow you to connect the plugin with your favorite mailer SMTPs and email automation tools so that you can simplify workflows and grow your business. Sendinblue Build customer relationships with an all-in-one digital marketing toolbox. Mandrill Start sending emails with Mandrill's quick-start SMTP Integration. gmail-logo Gmail Google Gmail is an email service developed by the company Google. Mailgun Mailgun's email API service helps you send, validate, and receive emails. SendGrid SendGrid uses cloud-based platform to deliver your transactional & marketing emails.