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Flight School Friday: Developing for deliverability

There are a number of API “hacks” that can be done to boost your deliverability rate.

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Last Friday, we talked about how marketers can use a reconfirmation email to clean their lists and improve deliverability. But don’t think you’re off the hook, developers.Deliverability is not just a term for marketers. There are a number of API “hacks” that can be done to boost your deliverability rate.

But first, what exactly is deliverability? It’s the number of emails that are successfully delivered into the inbox. The higher your rate, the more customers you are reaching. There are many factors that play into the success of an email landing in the inbox - ISPs, throttling, bounces and being marked as spam. A high deliverability rate requires being on top of latest email trends as well as regular maintenance. But more importantly, it takes a lot of teamwork and communication between your deliverability, marketing and IT teams.

Here are some API use cases that your team can set in place to help automate the deliverability process:

**Remove bounced addresses**

Use Mailjet’s Event API to track and remove bounced addresses from your contact list:

1. Create a webhook. This tracks all of the important email KPIs (clicks, opens, bounces) and does a post request each time a customer interacts with your email.

2. Then, do a call to our API to remove bounced email addresses from your master list.

A high bounce rate can damage your sender reputation with ISPs, because it typically indicates that you might be practicing spammer behavior. There are a variety of reasons why an email might bounce; a more legitimate reason being that a customer mistyped their email address, but other times you’ve emailed a spam trap. A spam trap is when ISPs recycle an old, inactive email address that is no longer in use to catch spammers that buy or rent old email lists.

Even if you are following best practices, when a customer opts-in to your mailing list and stops using their email address or switches over to a new address, you can potentially fall into this trap. Regularly cleaning your lists will help sweep for these inactive email addresses.

**Create rules & segment**

Even better, combine the Event API and Send API to segment inactive customers and re-engage them with a triggered email. Using the Event API, you can create rules to automatically filter out inactive customers (typically customers who have not opened or clicked an email in the past 3 - 6 months) and then connect this to the Send API to send a “We’ve Missed You!” email.

Re-engaging customers will not only lower spam complaint rates, but also helps you leverage untapped revenue. The average unsubscribe rate is 20% - of this percentage, there are customers that might simply just be overwhelmed with a full inbox or have forgotten the value of subscribing to your emails.


Using the Send API, you can create rules to personalize emails with customer data. Code emails to address a customer by name in the subject line, or refer to their last purchase/action on your site.

To personalize, be sure that you are already tracking this customer data somewhere in the sign-up funnel and that your email lists are well organized before you upload them onto your account.

Personalizing emails with customer-specific content will drive higher opens and clicks, resulting in a higher sender reputation with ISPs.

Let us know what other API “hacks” you’ve used!

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