Subaccounts, Custom Reverse DNS, Bounce Forwarding, and More SMTP Event Details

We have some major new features for you this week. Subaccounts let you manage and control your own users' email, Custom Reverse DNS lets you fully whitelabel your dedicated IP addresses, and Bounce Forwarding lets you integrate Mandrill's bounce handling with third party systems without using webhooks. Finally, SMTP Events now have more detail to help you troubleshoot delivery issues.


One of the biggest challenges of running an email service is the anti-abuse system. It only takes a handful of bad users sending spam to cause everybody's messages to be delayed or even blocked. Mandrill's reputation and quota system works well to protect Mandrill users from each other, but if you have multiple users of your own sending through a single account, sending for all of your users could be impacted by one or two less-than-stellar users in your account. Subaccounts let you leverage Mandrill's reputation system for your own users' email. Here's how it works:

First, you must create a subaccount for each of your users (or however else you want to split your mail). The subaccount must exist before you can use it to send mail, so we recommend that you create them using the Mandrill API as part of your own signup process.

Once that's done, you'll see subaccount stats start to aggregate in the Subaccount and Activity views. Each subaccount has its own quota that, by default, is managed by Mandrill in the exact same way we manage our own users. If one of your users starts misbehaving, we'll lower their subaccount quota to limit the damage they can do to your account's overall reputation.

You can set up alerts to monitor subaccount reputation, so if a subaccount's reputation drops to poor levels, you could contact them directly for remediation, or shut them down completely. You can find more information on what subaccounts are and how to get them set up in the Mandrill docs.

Custom Reverse DNS

You can now whitelabel the domain name associated with dedicated IP addresses. This allows more control over your sender reputation by making it clear to ISPs that an IP is associated with you and only you.

Setting up custom reverse DNS for your dedicated IP is easy - all you have to do is set up an A record pointing at your dedicated IP, and then use the Dedicated IP Management Page to configure Mandrill to use the new name. If you have multiple dedicated IPs, you'll want to set up a separate subdomain for each IP. We'll take the dedicated IP offline for 24 hours while the reverse DNS change propagates and then automatically reenable it when everything's ready.

Bounce Forwarding

Any time a message bounces, the mail server that detects the bounce sends a delivery status notification (or DSN) back to the sender. Mandrill uses these notifications to process bounces and record them in your account. To make it easier to integrate existing third-party applications that can also process bounce messages, we've added the ability to forward all of your account's bounces to a specific email address.

SMTP Event Details

We've added a few new fields to the smtp events log for messages. In addition to the response we received when we delivered (or tried to deliver) the message, we now log the IP we sent the message from, the IP we connected to in order to deliver it, and the size of the message. We're big proponents of making our sending and logging as transparent as possible, since every additional bit of data makes it easier to spot trends and diagnose problems. The SMTP events are also all searchable in your outbound activity.