Handy "How Tos"

How to find which ESP was used to send a marketing email.

  Gregg Blanchard     January 30, 2024    

It's a common question, right? You get a great email from a brand you admire or compete with, you're wondering what email marketing tool / ESP they used to send it but...how do you figure that out? It's one thing when the marketing tool they're using includes a "powered by" or logo at the bottom, but in all the other cases how do you figure out something that's really intended to be visible to us email recipients?

Within about a week of launching SendView back in 2016 this quickly became the most requested feature by a long shot and training our system to identify the ESP behind marking emails became a quest that we've gotten really good at over the years.

With that experience behind us, here are three approaches to finding which ESP was used to send a marketing email..

1) Search for Clues in Links / Headers

This is something you've probably already done, but let's dig into this a little bit more. One of the best things you can use to identify the ESP of an email is the unsubscribe link or "view in browser" link. If there's any link that ends up not being whitelabeled with the sender's own domain, one of these two is usually it. For example, in an email I just received all of the normal links showed the brand's domain. But when I hovered over the unsubscribe link and this was the URL:


Head to that root domain - madmimi.com - and you're realize that's the ESP. Pretty slick. Another place to look is in the headers of your email. You can see the headers by uploading the EML file to our EML viewer tool. For example, another email I just received had this clue in the unsubscribe header:

List-Unsubscribe: , <https://hs-4566937.s.hubspotemail.net…

If you can't find the ESP's name or domain in the unsubscribe link, try searching the HTML code for clues. Specifically, look at the image URLs. These aren't visible to the recipient and so sometimes an ESP will keep those on a generic domain rather than whitelabel it.

I'm not gonna lie, it can be really challenging to find the ESPs this way. Sometimes the clues are just below the surface and sometime's they're realllly deep. But if you're creative and determined, the data is often hidden in there.

2) Forward Emails to esp@sendview.io

Luckily, we've also built an easier way to do this that we call ESP Finder. Instead of downloading that email and digging through the code, you can just forward that email to esp@sendview.io and a few seconds later it will reply with the ESP used to send that campaign.

gif of how esp finder tool works

Now, a forwarded email does not include the original headers and such, so it's not as accurate as the last option I'll cover in a minute, but it can identify the ESP of roughly 90% of email campaigns. It can identify all the common ESPs like MailChimp, Constant Contact, Hubspot, and Klaviyo as well as lesser-known ESPs platforms like Invio, Privy, SmartrMail, and Loops.

And it's fast and free, which is definitely a bonus. One of the most popular aspects of ESP Finder, however, is the fact that you don't have to leave your inbox to find which ESP sent that email you're looking at. There's not software to install, there's no site to log into, you just hit forward...wait a few seconds...and you'll have your answer.

3) SendView ESP Identification

The good news, though, is that as I mentioned earlier, ESP identification was a heavily requested feature early on in the days of SendView and we not only shipped it quickly, but have continued to refine it over the years. In other words, ESP identification is baked right into the platform. If you sign up for emails using your SendView account, you'll see the ESP for (almost) every one.

Right now, SendView can identify emails sent from over 300 different ESPs. You can see this in a bunch of places throughout the app including the Inbox (you can toggle ESP as a column in your inbox along with other insights like word count, Gmail Annotations, dark mode, spam score, and more).

screenshot of esp flagging in sendgrid inbox

ESP insights are also visible in many other parts of the app including:

  • Individual emails view - look in the bottom left to see the ESP
  • Timelines - ever email detail will include the ESP
  • Collections - clicking on an email will show full details including ESP
  • Trend reports - there's a special report showing ESP usage by your competitors
ESP usage trend report screenshot

We've actually been able to take this feature one step further recently to flag when one of your competitors changes their email marketing platform or starts using a new ESP to send a specific type of campaign (like abandoned cart, confirmations, webinar emails, shipping updates, etc.. This helps you identify when a competitor is using a different ESP for specific types of transactional or automated emails, or when they switch completely to a new platform.

You can see these ESP activity notifications in your Alerts feed and you can filter only these alerts out using the dropdown at the top.

esp identification alerts in sendview

Three Ways to Find the ESP

So, there you have it. Three ways to find the ESP of the marketing emails you receive or your competitors and peers are sending:

  • Manually dig into the code for clues about which platform was used
  • Forward emails to ESP Finder and get an answer in about 10 seconds
  • Use SendView and the ESP is automatically identified and shown through the app

Like I said, it's not the easiest thing to find manually and ESP Finder does a good job of simplifying the process for emails you've already subscribed to with your personal address, but SendView is a great way to keep tabs on all the ESP-related activity among your competitive set. Our ability to identify which ESP sent an email and alert you when your competitors use new ESPs or change email marketing platforms is tough to beat.

No matter which solution you use, best of luck and enjoy your new found insight into the ESPs used to send the marketing emails you're subscribed to! And if you want to try SendView to see how our ESP identification tech works? Just start a free trial.