Postmark helps deliver and track transactional emails for web applications. In a nutshell, the service replaces SMTP (or Sendmail) with a far more reliable, scalable and care-free environment.
From its developer site:
Postmark helps deliver and track transactional emails for web applications. In a nutshell, the service replaces SMTP (or Sendmail) with a far more reliable, scalable and care-free environment. In addition, you can track statistics such as number of emails sent or processed, opens, bounces and spam complaints.