Sublime Security Raises $150M Series C to Expand AI Email Defense Platform

Washington-based Sublime Security has raised $150 million in Series C funding led by Georgian announced in a press release, with participation from Avenir, 01A, and existing investors Index Ventures, IVP, Citi Ventures, and Slow Ventures.

The company said it will use the investment to expand its AI-native email security platform and enhance its suite of autonomous agents designed to detect and respond to threats in real time. Sublime’s platform employs specialized AI agents that automate protection, triage, and adaptive defense tasks to reduce manual workloads for security teams.

Recent product additions include the Autonomous Security Analyst, which investigates and triages threats in seconds, and the Autonomous Detection Engineer, which deploys new defenses against emerging attacks within hours. Sublime reported 100% growth in annual recurring revenue in the first half of 2025 and has retained all enterprise customers since launch, including Spotify, Snowflake, and Zscaler.

The company plans to use the new funding to further develop its agentic AI capabilities and expand its global operations.