Handy "How Tos"

How to find the ESP that 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.

1) Look 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…

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.

And it's fast and free, which is definitely a bonus.

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. 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.

screenshot of esp flagging in sendgrid inbox

We've actually been able to take this feature one step further recently to flag when one of your competitors changes their ESP or starts using a new ESP. You can see this in your Alerts feed.

esp identification alerts in sendview

So, there you have it. Three ways to find the ESP of the emails you receive:

  • Manually dig into the code for clues
  • Forward emails to ESP Finder
  • Use SendView and the ESP is automatically identified

Best of luck!