Artificial intelligence-based email security startup StrongestLayer Inc. revealed today that it has raised $4.1 million in new funding to expand its platform and go-to-market push ahead of a planned Series A round.

Founded in 2024, StrongestLayer offers software that skips the signatures, reputation databases and past-attack patterns that most email security relies on. Instead, it reads a message and works out the intent behind it, then rules on whether the note is genuine or built to deceive. The company said that lets it flag attacks it has never encountered, since the call rests on context, not a prior match.

The target is a class of threats that slips past older products. StrongestLayer said it examined thousands of detections at customer sites from December through February and found that pattern-matching and behavioral filters, the backbone of most email security, could not reliably catch more than a third of the attacks landing in inboxes.

Many of the costliest ones carry no malicious link or attachment. A business email compromise or an executive impersonation scam can be in plain text, written to read as legitimate so that a person acts on it.

“Every generation of email security was built to recognize attacks it had seen before,” said Alan LeFort, StrongestLayer’s co-founder and chief executive. “That worked when attackers reused templates and infrastructure. It does not work when every attack is unique. We didn’t build a better filter. We built a system that reasons about whether a message is legitimate and whether it intends harm.”

StrongestLayer said production deployments have grown more than eightfold since its first round a year ago and that the platform has beaten both legacy secure email gateways and newer AI-branded rivals in competitive evaluations. Its threat research, including a taxonomy of 44 email attack subtypes, is posted at tools.strongestlayer.org.

Inovia Capital Inc. led the new round. Existing investor Sorenson Capital returned, joined by new backers LaunchPod, Alumni Ventures Group and Chris Key, former chief product officer of Mandiant. Taha Mubashir, a partner at Inovia, said the firm invested because the startup had done more with less. StrongestLayer reached a point where it could challenge entrenched vendors on a fraction of the money such companies usually spend to reach the market, he said.

Sorenson also led the company’s first round, a $5.2 million raise announced in July 2025. StrongestLayer has now raised $9.3 million in total.

Image: StrongestLayer