Mandrill—A Free SMTP Server for Applications

by Eugene MelnikovApril 22, 2013
This blog post provide an overview of Mandrill: its capabilities around e-mails campaigns, under-the-hood mechanisms, pricing models, etc.

What Mandrill offers

Transactional e-mails are important part of any project or business, no matter if it’s a startup or a big company. However, while corporations can afford the huge mailouts and the costs of big mail distribution services, startups usually look for cheaper options.

Mandrill by MailChimp is one of such options. It is a transactional mail distribution service that allows for sending up to 12,000 free e-mails per month. All you need is change SMTP credentials in your application or e-mail client. If you need more, there are various affordable pricing options. You can merge your MailCimp and Mandrill account and get some discounts.

Mandrill supports SPF and DKIM records ensuring your e-mails won’t be regarded as spam by the most of e-mail services. Furthermore, it allows for tracking e-mail statuses, such as sent, bounced, received, clicked, marked as spam, etc.


The functionality available

There is a reputation level and abuse detection heuristics for each account, so your account may not send real e-mails. In this case, you will get a notification ‘Message not sent: queued.’ In addition, make sure that you use correct ‘From’ header in you application, because e-mail from ‘root@localhost’ won’t be sent, but will be from ‘’ Even if you have a wrong ‘From’ address or sending e-mails is paused, your application won’t get any errors if you use just SMTP. You will just see successful API calls. If you really want to know the status of an e-mail, you may use webhooks. There is a gem for Ruby on Rails that add support for webhooks. The following hooks are available:

  • Message is sent.
  • Message is bounced.
  • Message is soft-bounced.
  • Message is opened.
  • Message is clicked.
  • Message is marked as spam.
  • Message recipient unsubscribes.
  • Message is rejected.

Mandrill can change you e-mails before sending. It allows for tracking some actions, enhancing e-mails, and even adding a unsubscribe link. Mandrill supports templates and special tags for A/B testing.

There is search by subject and recipient address with an ability to filter by status and export found data. To keep you up-to-date on all your account activity you can install application for your Android.

The same is applicable for iOS.

Finally, Mandrill has great RESTful API. It allows you to do everything and even try requests directly in the documentation. Using API is the most efficient way to control your mailing. There is a gem available for this API.

Hope it helps someone to choose the right solution.


Further reading