How Inboxbooster Plans To Keep Your Emails Out Of The Spam Folder

The spam folder in your email application is a lifesaver, screening out tonnes of junk messages you don’t want to waste your time with. But are legitimate emailers also struggling to make it past your filter, meaning you miss out on messages you actually want to see? California-based start-up Inboxbooster, which is today announcing a $1 million funding round, says its technology can help.

“It’s a problem affecting everyone,” says Inboxbooster co-founder Nicolas Toper. “If you send an email, you can’t be sure it hasn’t ended up in the recipient’s spam folder; if you email a group of people, you’ve no way of knowing how many of your messages got through to their inboxes.”

In fact, says Inboxbooster, as many as 85% of email messages end up in people’s spam folders – and are therefore destined never to be read. That includes a huge number of unwanted marketing emails and sales round robins, which recipients will be delighted to avoid. But it also includes many important messages – everything from personal messages and invites to payment notifications and official notices.

Inboxbooster’s technology is therefore aimed at email senders. For any given email, it will tell you how likely the message is to end up in a spam folder, which attributes of the message are increasing its chances of going straight to junk, and how to change the email to improve the odds of it making it into the recipient’s inbox.

“No one wants their email to end up in spam but avoiding it can be more difficult than you would think,” says Toper. “Inboxbooster accurately tells you why you’re in the spam or promotions folder and what to do to move back to the inbox.”

To provide that diagnosis, Inboxbooster’s technology trained on a dataset of 100 million emails, analysing what made them more likely to end up in spam. The parameters taken into account by email solutions such as Gmail and Outlook are far more varied than most people realise, Toper explains. They include everything from security red flags to the content of the message.

Importantly, Toper insists that Inboxbooster is not aimed at marketing companies hoping to get more of their unsolicited email campaigns through to potential customers. “We’re not circumventing the spam filter,” he says. “If that’s the kind of email you’re sending, the reason you’ll end up in spam is because people don’t want to receive your message.”

Rather, Inboxbooster is focused on small businesses and individuals – large companies have often developed their own inhouse tools to improve their email penetration rates, Toper explains. For example, the company works with firms struggling to get invoices paid because their emails requesting that a bill is settled haven’t gone through. It points to examples of couples who have failed to get wedding invites to everyone meant to receive them.

In line with that value proposition, Inboxbooster offers its tools for free to those using them on a one-off basis, though people are invited to make a voluntary contribution to its costs. To monetise the service, the company also offers a subscription model for regular users who need to use the tools more systematically. So far, the company has signed up around 3,000 users.

Toper believes the technology has huge appeal. “In five years’ time, everyone is going to be using a service like this,” he argues. “Email is the only open communication left and it is important to preserve this and make it accessible to all.”

The company’s early-stage funding should help it make a play for a share of this growing market as it comes out of stealth mode and begins marketing its solution more widely. The $1 million of pre-seed funding is coming from the start-up accelerator Y Combinator and a number of prominent business angels.

Y Combinator’s involvement brings Inboxbooster full circle. The company was born out of Toper’s collaboration with co-founder Marcus Engene at a three-month Y Combinator programme in 2020. The duo noticed that the accelerator’s weekly newsletter was routinely ending up in people’s spam folders, so they built a tool to address the issue, improving the email’s click rate by 35%.

“We are filling a significant gap in the market for others because no other solution fixes the problem in the same way,” says Toper, who saw the appeal of that original tool for a broader audience. “This is a real and painful issue for many.”