In today’s digital world, an email that appears too perfect can actually work against you. With tools like ChatGPT and Gemini making it effortless to generate clean, structured messages, accuracy is no longer a reliable signal of skill or sincerity. Instead, it can suggest minimal effort and complete reliance on AI.
As a result, communication norms are shifting in an unexpected direction. Small mistakes -typos, casual phrasing, even all-lowercase messages – are increasingly being interpreted as proof that a real person took the time to write the email.
What once signaled carelessness is now, in some circles, seen as authenticity and even authority. The rules of ‘good writing’ in private communication appear to be undergoing a dramatic reset.
This changing mindset has even led to the creation of tools designed to reintroduce imperfection into otherwise polished text. One such example is Sincerely, a Chrome extension developed by Ben Horwitz. The plugin intentionally alters emails by adding mistakes and stylistic quirks, making them appear more human.
In a post on
I made the anti-Grammarly. Mess up your emails with AI. https://t.co/R6kdTpoc0W pic.twitter.com/1AF5qrCFwT
— Ben Horwitz (@horwitzben) April 23, 2026
How does it work?
Sincerely operates through three modes. The ‘Subtle’ option removes filler words and introduces contractions, often inserting a minor typo early in the message. The ‘Human’ mode goes further, creating a more conversational tone while still adding imperfections.
The most distinct setting, ‘CEO,’ produces extremely brief, lowercase emails, sometimes even appending “sent from my iPhone”, to mimic the fast, minimal communication style often associated with top executives.
Sincerely was created as a ‘fun’ experiment, says Ben Horwitz
Horwitz, who built the tool using Claude, says the idea came from his personal experience. Describing himself as a slow typist and mildly dyslexic, he recalls spending significant time early in his career ensuring emails were error-free.
We can add this line. Ben Horwitz, an investment partner at venture capital firm Dorm Room Fund, created Sincerely, according to the website.
“I am a terrible typist, naturally, and mildly dyslexic. It would take me so long in my first job straight out of college to write emails and make sure there were no typos and everything. When Grammarly came around, it was like, ‘Oh, OK, this is pretty good for me.’ But now my email inbox is filled with AI slop,” says Horwitz, who is about to graduate from Harvard Business School.
He maintains that Sincerely was created as a ‘fun’ experiment rather than a serious commercial product. Although the plugin charges a small fee after limited free use, Horwitz has suggested his primary interest lies in exploring and poking fun at business life.
Sincerely offers limited free usage, allowing users to rewrite up to three emails directly within Gmail. For those opting for the paid version at $4.99 per month, the tool provides unlimited rewrites, quick switching between different modes, and a caching feature that lets users instantly access previously generated results.
“I love making products that make people think twice about technology. And in this case, it’s also a little bit like the pushback on how we’re using technology today. So, you know, there’s a $4.99 a month model that if you want to not bring your own key, you can pay me. I think it’s probably double digit people who are paying and not using their own key, but it could be a business,” he told TBPN.
Here is how to activate it:Install from Web Store: Go to the Chrome Web Store, search for ‘Sincerely,’ and select Add to Chrome.
Locate Extension: Click the Extensions icon in the top-right corner of Chrome.
Pin: Find ‘Sincerely’ and click the pin icon to make it visible in the toolbar for quick access.
Manage Permissions: If prompted, grant the extension access to read and change data on websites.
Toggle Activation: If the extension is not working, go to the Chrome extension and toggle the switch to the ‘On’ position.
