ABNORMAL SECURITY

Evan Reiser and Sanjay Jeyakumar both worked on machine learning for Twitter's ad products, where the job was catching fake ad clicks and abuse. They realized the same behavioral modeling could catch fake emails.

Business email compromise, where a crook impersonates a boss or a supplier to get money wired, is the most financially damaging cybercrime the FBI tracks, yet most email security tools just look for malicious links and attachments. They founded Abnormal in 2018 to apply behavioral AI to the problem.

In 2025 the company renamed itself Abnormal AI to signal it is more than an email filter.

Abnormal Security uses AI to stop email attacks that traditional security misses — business email compromise (BEC), social engineering, vendor fraud, and account takeover. Instead of scanning for malware or known phishing links, Abnormal builds a behavioral model of every person in the organization: who they email, what they talk about, how they write, when they work.

When an email deviates from that pattern — like the CEO suddenly asking for a wire transfer at 2 AM from a weird IP — Abnormal flags it. Subscription-based, priced per mailbox per month.

Integrates directly with Microsoft 365 and Google Workspace via API.

Abnormal Inbound Email Security, Abnormal Email Account Takeover Protection, Abnormal Security Posture Management, Abnormal AI Security Mailbox

Land with email, expand into platform. Abnormal started with inbound email security and has built out into account takeover protection, security posture management and AI-powered security operations.

It crossed $200 million in annual recurring revenue around its August 2024 Series D, which valued it at $5.1 billion, and says it serves thousands of customers including a big slice of the Fortune 500. In 2025 it rebranded as Abnormal AI and hired a public-company CFO, which is the usual signal that an IPO is being prepared.

Competing for budget against Microsoft's built-in email security (Defender for Office 365) and established players like Proofpoint and Mimecast. Many security chiefs wonder why they need a third-party email tool when Microsoft keeps improving its own.

Abnormal has to keep proving that behavioral AI catches attacks Microsoft misses. The other challenge is expanding beyond email into identity and AI security without losing focus, at a valuation that assumes it will.

Greylock Partners led the $24 million Series A in November 2019. Menlo Ventures led the $50 million Series B in 2020.

Insight Partners led the $210 million Series C in May 2022 at a $4 billion valuation. Wellington Management led the $250 million Series D in August 2024 at $5.1 billion, with Greylock, Menlo, Insight and CrowdStrike's Falcon Fund joining.

Total raised is about $546 million.