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Email security

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Stop BEC, invoice fraud, and executive impersonation

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Protect against calendar phishing attacks

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Shut down prompt injection attacks

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Invoice fraud campaign adds prompt injection aimed at email AI agents

Invoice fraud emails hid Unicode tag prompts telling AI agents to forward the invoice to accounts payable.

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Secure the Agentic Inbox

Sublime detects prompt injection in email before it reaches your AI assistants and agents. No integration with the agent required.

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billing@northwind-supply.example

Updated invoice for March

Hi Maya, the March invoice is attached.

Please process it by Friday.

Invoice-March.pdf

Best, Alex Chen

Accounts Receivable · Northwind Supply Co.

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AI connected to your email creates a new vulnerability

A trusted assistant that follows an attacker’s instructions can expose data, approve fraud, or reset accounts.

AI assistants can act on an attacker’s instructions

A malicious email can redirect an assistant into leaking mailbox data, forwarding or deleting messages, or approving a fraudulent refund.

Your employees can’t see the payload

Instructions hidden in HTML, white-on-white text, or obfuscated content can be ready by an assistant even when the email looks ok to a person.

Suspicious language isn’t always an attack

AI tutorials, research, and security discussions use the same phrases as malicious instructions, so keyword rules alone are not effective.

Detection built for how AI reads email

Inspectable logic, automated investigation, and controls your team can shape.

Covers sanctioned and shadow agents

Prompt injection detection is on by default for every maibox, covering agents you know about, and the ones you don't.

Detection logic you can read and adjust on-demand

Detections are transparent and auditable, so you see why every message was flagged for prompt injection, and make adjustments if you need to.

Agentic investigation on every match

ASA investigates each flagged email and assigns a verdict, separating real attacks from legitimate instructions.

Measure prompt injection activity over time

Track prompt injection activity alongside your other email threats.

Enable AI assistant adoption with confidence

Detection at the email layer, investigation by the Autonomous Security Analyst (ASA), and logic your team controls.

Protect AI-connected inboxes

Reduce exposure to email-borne instructions that try to manipulate assistants and agents into leaking data or taking fraudulent actions.

Avoid disrupting AI productivity

Pair machine learning (ML) detection and targeted detection logic with Autonomous Security Analyst (ASA) investigation to tell real attacks from legitimate email content.

Customize your coverage

Out of the box prompt-injection detection logic can be tailored to how your organization uses AI-connected inboxes.

See Email Prompt Injection in action

What our customers are saying

The black box approach to email security no longer works. 
It reduces visibility on how 
Brex may be attacked and 
the tactics and techniques 
used by attackers. 



With Sublime, we now have transparency and the confidence to keep up with emerging threats.

Mark Hillick

Mark Hillick

CISO, Brex

The ability to automate remediations with high confidence and minimize manual reviews unlocks a new level of efficiency in our SOC. It’s hard to imagine going back to life before Sublime.

JJ Agha

JJ Agha

CISO, Fanduel

What I love about the platform is that it just works. I’m so tired of all these tools I have to futz with, and Sublime is just easy.

Jason Kikta

Jason Kikta

CISO, Automox

With Sublime, we no longer wait weeks for vendor updates. Our team reacts instantly - which is critical for our fast-moving environment.

Ronald Richards

Ronald Richards

OVO Energy

See all customer stories

Frequently asked questions

What is prompt injection in email?

It’s an email with instructions meant for an AI assistant or agent instead of the person reading it. If the assistant acts on them, it could expose mailbox data, forward or delete messages, or approve a fraudulent refund.

Is Prompt Injection Detection available now, and what plan is required?

Prompt injection detection is generally available. It’s included in the Sublime Enterprise plan.

How is this different from keyword or phrase matching?

Phrase matching alone is brittle, because legitimate AI tutorials and security research use the same words as attacks. Sublime combines targeted rules and machine learning (ML) to flag potential attacks. The Autonomous Security Analyst (ASA) then investigates each match and assigns a verdict.

Do we need to integrate with our AI tools or agents?

No. Sublime detects prompt injection at the email layer, so nothing needs to connect to the agent.

Can we see and change the detection logic?

Yes. You can inspect and extend the detection logic to fit how your organization uses AI-connected inboxes.

Do I need to know which mailboxes use an AI agent to get this protection?

No. Prompt injection detection works at the email layer, so it applies to messages Sublime already scans, with no agent integration or mailbox-by-mailbox setup.

Now is the time

See how Sublime delivers autonomous protection by default, with control on demand.

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