Best Email Security Tools Across Inbox, Gateway, and Auth
API desks, MX gateways, report buttons, and DMARC are different jobs.
Proofpoint’s 2024 phishing-simulation data puts the average employee reporting rate at 18.65% across more than 212 million test messages.
That means most users never press the report button even when the message is a known fake. The ones who do still land in an abuse mailbox that a SOC has to clear. A green gateway dashboard does not empty that queue.
Email security is not one product. Domain authentication refuses exact-domain spoofing. A secure email gateway filters the MX hop. An API desk reads the cloud mailbox after delivery for BEC that already passed SPF. A reporting platform turns the employee click into remediation. The dedicated gateway cut lives on secure email gateways. The move to p=reject lives on DMARC tools.
This shortlist picks one seat for each of those jobs: behavioral API inbox defense, a commercial SEG, an API/inline collab desk, transparent BEC detection, employee report automation, and domain authentication.
How we evaluated
We read first-party product pages, pricing CTAs, licenses, and docs. We asked whether the product sits on MX or on a mailbox API, whether BEC and impersonation are a named job, whether employee reports become automated remediation, and whether domain authentication is the control or a side module. Marketing pages count as claims, not as proof two tools do the same work.
| Tool | Best for | What to check |
|---|---|---|
| Abnormal AI | API behavioral defense for BEC and vendor fraud | Commercial · M365/Google API · no MX |
| Proofpoint | Commercial SEG with optional API path | Commercial · MX or API · enterprise desk |
| Check Point Harmony Email | API/inline inbox plus collaboration apps | Commercial · Avanan lineage · quote |
| Sublime Security | Transparent BEC detections operators can edit | Commercial · MQL rules · free tier path |
| IRONSCALES | Employee report button with automated remediation | Commercial · Outlook add-in · ICES |
| Valimail | Domain authentication toward p=reject | Commercial · Monitor free · Enforce paid |
Abnormal AI
Best for API behavioral defense against BEC and vendor fraud
Abnormal connects to Microsoft 365 or Google Workspace through APIs. It does not ask for an MX cutover. The product models people and vendor relationships, then remediates BEC, invoice fraud, account takeover, and payload-light social engineering that already passed authentication.
First-party pages also sell an AI Security Mailbox for user-reported mail and Detection 360 for missed-attack feedback into the models. That is the hosted conversation desk when the SEG already green-lit the thread.
Key features:
- Cloud-native API architecture for M365 and Google Workspace
- Behavioral baselines for employees and vendors
- Post-delivery remediation without MX changes
- AI Security Mailbox triage for employee reports
Why we like it:
When the failure mode is a real vendor mailbox or a lookalike wire request, an MX signature filter is the wrong layer. Abnormal is built for that conversation.
Limits:
Commercial, quote-only. API consent is a security review. It is not a substitute for publishing p=reject on your own domains.
License or pricing: Commercial. Demo and quote CTAs. No public per-mailbox list price on the pages we read.
Proofpoint
Best for a commercial SEG with an optional API path
Proofpoint Core Email Protection is the enterprise gateway most RFPs already name. First-party pages now document both SEG and Microsoft Graph API deployment, plus a Threat Protection Workbench and Satori abuse-mailbox automation.
If procurement already wrote Proofpoint into the path, tune that hop before stacking a second vendor for vanity. The deeper MX-versus-API cut for gateways sits on the dedicated secure email gateway shortlist.
Key features:
- SEG or API deployment for M365 and Google environments
- URL and attachment defenses with sandboxing stories
- Threat Interaction Map and SOC workbench
- Agentic review for user-reported mail (Satori)
Why we like it:
Honesty about the hop procurement already bought. Flexible deployment is useful when the estate mixes MX politics with cloud tenants.
Limits:
Commercial enterprise packaging. MX cutovers still take change windows. Public pages are not a lab scorecard.
License or pricing: Commercial. Sales-quoted. No public list price on the Core Email Protection page we read.
Check Point Harmony Email
Best for API or inline inbox defense that also covers collaboration apps
Harmony Email & Collaboration is the Avanan lineage product inside Check Point. It connects to Microsoft 365 and Google Workspace through APIs, with Monitor and Prevent (inline) enforcement modes documented in deployment guides.
The distinguishing job versus a pure BEC desk is collaboration coverage: Teams, Slack, OneDrive, and related SaaS surfaces sit in the same Email & Collaboration packages. Anti-phishing, URL protection, sandboxing, and DLP are package lines on the first-party plans page.
Key features:
- API connection with Monitor or Prevent modes
- Incoming and internal email anti-phishing
- Collaboration app coverage on Email & Collaboration packages
- Sandboxing, URL rewrite, and optional DLP tiers
Why we like it:
When the board asks for inbox plus Teams in one quote, Harmony is the Check Point answer that is not another MX-only SEG.
Limits:
Commercial channel pricing. Confirm Email Only versus Email & Collaboration on the quote. Not a DMARC operator.
License or pricing: Commercial, quote-based. First-party plans page lists Advanced Protect and Complete Protect packages without a public list rate.
Sublime Security
Best for transparent BEC detections operators can author and backtest
Sublime is the detection-engineering answer to black-box email verdicts. It connects to Microsoft 365 or Google Workspace via API, ships Message Query Language (MQL) rules, and markets ASA for abuse-mailbox triage plus ADE for org-specific detection authorship.
Community rules live under an MIT license on GitHub. Essential Protection documents a free path for the first 100 mailboxes; Autonomous Protection is quote or channel. The Material versus Sublime operator split is on Material vs Sublime.
Key features:
- API deployment without MX changes
- MQL detection rules with explainable matches
- ASA triage for user-reported mail
- ADE for backtested org-specific coverage
Why we like it:
When the SOC refuses to wait months for a vendor rule change, editable detections are the product.
Limits:
You still staff detection review if you turn the agents up. Self-hosted paths need Graph permissions you own. Not a classic SEG.
License or pricing: Essential Protection free for the first 100 mailboxes on first-party packaging we tracked. Autonomous Protection is demo or channel quote. Community rules MIT.
IRONSCALES
Best for employee reporting with automated remediation
IRONSCALES is the Integrated Cloud Email Security desk built around Adaptive AI plus an Outlook Report Phishing add-in. First-party pricing lists EmailEssentials, EmailProtect, and CompleteProtect paths, all without MX changes.
The job that earns the seat here is the report-to-remediate loop: employee flags a message, the platform clusters similar mailboxes, and Agentic remediation clears copies. Security awareness and phishing simulation sit as Human Risk Management add-ons, not as the whole product.
Key features:
- Report Phishing add-in for Outlook on M365 and Google endpoints
- Agentic autonomous remediation with tunable automation
- API deployment alongside an existing SEG
- Optional ATO protection and awareness modules
Why we like it:
When simulation programs raise reporting volume, someone has to empty the queue. IRONSCALES sells that response path without forcing an MX rip-and-replace.
Limits:
Commercial packaging with plan sprawl. Confirm whether you need Essentials automation or Protect scanning depth. Awareness modules are separate lines.
License or pricing: Commercial. Public plan names on ironscales.com/pricing. SMB buy-now and MSP packages; enterprise quotes for larger seats.
Valimail
Best for domain authentication on the path to p=reject
Valimail operates SPF, DKIM, and DMARC so your domains can refuse exact-domain spoofing. Monitor is free visibility. Enforce automates sender authorization, Instant SPF beyond the classic ten-lookup limit, and continuous enforcement reporting.
This is not an inbox content filter. Lookalike domains and compromised vendor threads still need the gateway or API desks above. The fuller reporter shortlist stays on DMARC tools.
Key features:
- Free Monitor for domain visibility
- Enforce automation toward continuous DMARC enforcement
- Instant SPF for the lookup limit
- BIMI Amplify add-on for brand indicators
Why we like it:
Authentication is still a DNS control. Valimail is the commercial operator most teams mean when they refuse to live on p=none forever.
Limits:
Does not stop cousin domains or payload phishing. Enforce pricing starts in the thousands per year. DigiCert acquired Valimail; confirm the live SKU name on the quote.
License or pricing: Monitor free. Enforce Starter listed from $5,000/year on the pricing page we read; Premium and Enterprise are contact-us.
How to choose an email security tool
Four questions before the quote. Names below are the shortlist, not a scored bake-off.
| Critical question | Why it matters | What to evaluate | Red flag |
|---|---|---|---|
| Does mail still hit an MX we own? | SEG and API desks deploy differently. | Proofpoint for MX or hybrid. Abnormal, Harmony, Sublime, IRONSCALES for API tenants. | An MX cutover sold into a pure M365 estate with no hop to move. |
| Is the hole a payload, a lookalike, or a real vendor thread? | Controls map to failure modes. | Gateway URL/attachment defenses for payloads. Valimail for exact-domain spoofing. Abnormal or Sublime for conversation BEC. | A DMARC dashboard sold as BEC coverage. |
| Who empties the abuse mailbox? | Reporting without remediation recreates the queue. | IRONSCALES report button plus automation. Abnormal AI Security Mailbox. Sublime ASA. Proofpoint Satori. | Awareness videos with no remediation path. |
| Are we still on p=none? | Monitor is not enforcement. | Valimail Enforce, or the dedicated DMARC tools shortlist. | BIMI logos before reject. |
What we left out
- Mimecast, Barracuda, Cisco Secure Email, Rspamd, SpamAssassin, and Microsoft Defender for Office 365: those seats belong on the secure email gateway list.
- dmarcian, EasyDMARC, OpenDMARC, MXToolbox, and Proofpoint Email Fraud Defense: those seats belong on DMARC tools.
- Material Security: strong ATO and Workspace recovery product. Paired with Sublime on the compare page rather than duplicated here.
What practitioners argue about email security
Live threads keep returning to the same split: authentication proves who sent the mail, but it does not prove the mail is safe. Gateways and API desks exist because SPF can pass and the invoice can still be wrong.
Hacker News · May 2025
“We have DMARC, DKIM, and SPF, and while this provides some signal with regards to mail origination, it falls flat when emails are being sent from Gmail, Yahoo, and other large service providers. This is why email security gateways exist.”
The dissenting beat in that Ask HN thread is that consumer Gmail already filters most junk into spam. Enterprise tenants still buy gateways because allowlisted business senders and BEC do not look like junk.
Information Security Stack Exchange · Jan 2023
“SPF, DKIM, and DMARC just tell you if the sender spoofed the domain or if a legitimate email was hijacked. They are not ‘security checks’.”
The question describes phish that passed every sender check from a legitimate company domain. That is the exact-gap Valimail cannot close alone and Abnormal or Sublime are bought to cover.
Information Security Stack Exchange · 2020
“Instead of deleting or rejecting the message, Office 365 marks the message as spam” when inbound mail fails a domain’s p=reject policy.
The Office 365 DMARC reject thread on Information Security Stack Exchange documents the oreject override. Publishing reject on your domain does not guarantee every receiver will refuse the message.
If the MX hop is still yours, start with Proofpoint or the gateway shortlist. If mail already lives in M365 and BEC is the pain, shortlist Abnormal, Harmony, or Sublime. Put IRONSCALES on the quote when the report button backlog is the morning queue. Keep Valimail or the DMARC list for the DNS job.
FAQs
Is this the same page as secure email gateway?
No. The gateway page is the MX and API filter cut with open filters and suite-native seats. This page is a cross-job shortlist across API inbox defense, SEG, BEC detection, employee reporting, and domain authentication.
Does Abnormal replace Proofpoint?
Sometimes. Abnormal markets SEG displacement for cloud tenants. Many estates still keep a gateway for pre-delivery policy and run an API desk for conversation BEC. Treat them as different architectures until the mail path says otherwise.
Is Valimail an inbox security product?
No. Valimail authenticates your sending domains. It does not inspect mailbox content. Use the DMARC tools list for more reporters.
Is this a scored bake-off?
No. Order is editorial.
