How do you setup MageMail to work with Mandrill?

Mar 9, 2016 Update: Due to Mandrill's policy changes, we're adding support for other transactional email services, and recommending people use Sendgrid instead of Mandrill - more details

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I tend to recommend that people use Mandrill for their email delivery. It's free for up to 12k emails / month which most of my customers don't max out, and it comes with a number of benefits:

- Helps with deliverability - Provides additional statistics / click / open tracking - Provides information on complaints (when someone marks an email as spam) which is very helpful to determine how customers are responding to email. - It reduces the load on your server because instead of MageMail making an API call to your server to send an email, it goes through Mandrill directly.

If you haven't created an account yet, you can create one at: https://mandrill.com/signup/

Once you've signed up, just grab your API key and drop it into the settings section of MageMail: