Bulk Validations — Accurate and Fast AF

Written by Alan Erwin

Categories: What's New

5 minute read time

Cleaning an old email list is one of those must needed chores that nobody really wants to do. You have to do it, but you push it back because other priorities pop up.

It’s easy to jump the gun and skip cleaning that list, but that’s only going to do more harm than good to your conversions. At that point, you finally sit down and start validating that list one entry at a time, address by address, in order to determine whether or not they’re real and legitimate inboxes.

While our email validations service worked well for validating email addresses on signup and lead forms, it was a little harder to use on a larger contact list. Running email after email manually, one by one, is time-consuming and tedious. We knew we could make this process easier, so we hopped on the phone with customers, compiled your feedback, and started making some big functionality improvements.

We’re thrilled to announce that bulk validations is now available! We wanted it to be faster than any other validation tool on the market with extremely accurate results based on what we’ve learned from sending billions of emails every week. And that was an interesting problem to solve.

Before we get ahead of ourselves though, let’s answer this:

Why validate in bulk?

Bulk validations as a concept is simple. Put an email list in, get results out (in this case, as a CSV or JSON file). These results allow businesses to clean their lists in order to better their email delivery and have clean data in general.

We’ve made the case before, but it’s important to remember how critical clean emails are for your deliverability. When you validate a batch of emails, ideally you take out the ones that are invalid or risky, leaving you with a list of contacts that are real and active. These recipients are more likely to engage with your emails, and removing invalid and disengaged emails helps reduce bounces and unsubscribes.

List cleaning should be done to just about any list you have at some point in time and then frequently revisited for optimal deliverability, especially since around 23% of email addresses change within a year. While the frequency of cleaning your list can vary depending on how often you send, we recommend that you clean your list at least once a quarter.

Still, what exactly makes something like bulk validations challenging?

Problem one: volume

With our single input validations, the issue lies in volume. When we get a new customer with a massive list, they’d have to run every single email through our validations tool. If that list contains millions of email addresses, that process would take forever under the old method. On top of everything else needed for an email campaign, that volume of validations can become distracting.

And then it looks kinda like this.

It’s much more challenging to implement a proper list cleaning cycle when it consumes a lot of your time and energy. Plenty of people deviate from the standard recommendation of quarterly list cleanings, relying instead on validations on forms or validating only newly acquired emails, but that isn’t ideal for sustainable deliverability.

If we can eliminate the time it takes to validate massive lists, businesses can begin implementing better list cleaning policies. And that means less sending to fake, old, or incorrect emails and more emails in the inbox.

Problem two: bandwidth

Let’s continue with our example of taking the single validation and applying it to a list of emails. When you validate an email address, the API will ping the inbox service provider and essentially ask: is this address real and is it legitimate? To do that, it needs the internet, and that’s a bit of a toss-up for several reasons.

First, there are internet speeds to deal with – how much bandwidth do we have at any given time? Second, how much of that bandwidth is going to other processes, and how much is left over for validating these emails? That bandwidth fluctuates depending on how many other processes are happening and any number of external factors like a slowdown of internet service or outage. A single customer trying to do this on their own likely doesn’t have the bandwidth or the time.

The solution — infrastructure

Our validations API could do the work, but we wanted to be sure it could handle both a small list of a couple hundred emails and a much more extensive list of hundreds of thousands at the same time with little slowdown.

To handle the problem of both volume and bandwidth, we built an entire backend job system to allow for the scaling of large amounts of validations.

How accurate is it?

This backend job system is backed by our sending infrastructure that sends out billions of emails each month, which adds a layer of accuracy that other validation providers lack.

As an ESP, all of our constant communication with ISPs allows us to know exactly which email addresses we send to are deliverable and which aren’t. Based on that feedback, we continually update the data, which gives you better, faster, more accurate results.

How fast is it?

Our email validation service is now the fastest in the industry, and we’ve got the numbers to prove it:

Email AddressesTime
10,0001 Minute
100,00010 Minutes
1,000,00060 Minutes
These are values under normal operating circumstances here at Mailgun.

Our system works to make sure that jobs are completed promptly without impacting other validation requests or API calls. Everything runs as it should, and you get results you can trust without having to wait a week.

Everybody wins

Now, let’s get into how you use it.

How to use Bulk Validations

Under the validations tab in the new UI, you will have the option of running a single validation or uploading a file for bulk validation. In order to upload your list, it must be a CSV file and have email as the column header.

Once uploaded, our API gets to work validating your emails. In the new iteration of validations, we make it a lot easier to decide who you should and shouldn’t send to. You’ll get a risk score alongside a deliverable result for each email address on your list, so you can quickly determine whether or not the email is safe for sending. After every email address on your list has been validated, you can download your results as either a CSV file or a JSON file, whichever you prefer.

Please note that the results of your bulk validation will be available for download for 30 days after processing is complete. Setting a limit on how long your results are available keeps you safe from using old data and potentially harming your deliverability. It would be a nightmare if someone in your org pulled old results and used them as an email list unintentionally.

Still, be sure to save the results file should you need it past the 30 days.

We should also add that even though we’ve added more functionality, we’ve kept the cost of our validation service the same. For those with large lists, reach out to us so we can help you find the best pricing option for the results you’re looking for.

See how it works

Since this is new and newness can be scary, we’ve made a screencast that dives into some of the finer details of our new bulk validation service and provides a nice, in-depth walkthrough.

Building onwards and upwards

All in all, this is a great addition to our new validations API and UI as it helps provide a better platform for deliverability and sending as a whole. Our validations tool has always been a piece in the puzzle of email solutions we offer like our managed deliverability service and sending API, but now it takes on a more significant role by providing sound advice on whether or not to send, and it can tackle lists on a much larger scale at incredibly fast speed.


If you have more questions in regards to pricing and how bulk validations can work for your business, reach out! We’d love to figure out a solution for you.

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Modified on: May 17, 2019

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