How does inboxbooster work?

We provide evidence-based answers to why your email is in spam

How to work with Inboxbooster?

step 1


Test any new templates or campaign with Inboxbooster.

step 2


If your emails land in spam or promotion, Inboxbooster will diagnose the surface and the root causes.

step 3


Implement the changes recommended by Inboxbooster.

step 4


Usually, deliverability issues are fixed after 2-3 cycles with different problems detected and fixed with Inboxbooster.

Why Inboxbooster?


When you send too many times to a test address, the spam filter infers what the address likes to receives. This training effect corrupts most inbox placement tests on the market. Using our patented algorithm, we ensure the addresses we utilize stay ‘neutral’. That’s why we only need two addresses for our tests.

We systematically alter various components of your email to identify precisely why it lands in the spam folder. By using our patented algorithm, we pinpoint the root cause of your deliverability issue.

Our iterative approach queries spam filters to understand why your emails end up in spam. That’s why every solution we provide is backed by concrete evidence.

Sending emails to the inbox is a science not an art. There  is always a solution. Inboxbooster will find it for you.


We built Inboxbooster on the idea that if we help users understand why they’re in spam, they can fix their emails, and stay in inbox.

About Us

We are a proud three-person company.

Nicolas Toper


Nicolas is a deliverability expert with over 20 years of experience. He co-founded an email delivery company and delivered more than 50 0 billion emails.

Marcus Engene


Marcus is a recognized CTO who co-founded Pond5, a company acquired for 200M$ by ShutterStock. He holds several key patents in visual machine learning.

Zach Cohen

Customer Success

My name is Zach and I’m a dedicated customer success specialist who is here to help you with your deliverability issues! I've worked previously with customers in education and recruiting and look forward to bringing my experience to the deliverability space. Run a free inbox placement test at and let’s discuss your results!