SEG Detection

Secure Email Gateway Detection for Cold Outreach

Check If a Domain Uses Proofpoint, Mimecast, Barracuda, or Other SEGs

Secure email gateways (SEGs) silently filter cold outreach. MailRook detects 10 email security providers via MX record analysis and tells you the protection level of every email address — so you can prioritize prospects most likely to see your message.

Start Detecting Free
10 enterprise gateways detected
Included in every validation
100 free checks per day
Check in progress...
What we check
Valid format
Domain
Deliverable
No catch-all
Generic
Not Disposable
Company Email
Not University
The Problem

Why SEG Detection Matters for Cold Email Deliverability

Secure email gateways are the #1 silent killer of cold outreach. Your emails pass SPF, DKIM, and DMARC — but the gateway still filters them. Knowing which prospects are behind a SEG lets you skip, deprioritize, or adapt your approach.

76%

Filtered by Gateways

Cold emails to enterprise-protected inboxes face aggressive content scanning, reputation checks, and behavioral analysis beyond standard spam filters.

3x

Higher Reply Rates

Prioritizing unprotected inboxes means your emails actually land. Focus outreach volume where it has the highest chance of being seen.

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Know Before You Send

Every email validation returns protection level and detected gateways. No extra API calls — it's built into every check.

Detection

10 Secure Email Gateways We Detect

MailRook checks MX records in real time and identifies which email security provider protects each domain — so you know before you send.

Proofpoint
Proofpoint

Enterprise email security gateway with advanced threat protection.

Mimecast
Mimecast

Cloud email security platform with threat protection and archiving.

Barracuda
Barracuda

Email security gateway with spam filtering and data protection.

Cisco Secure Email
Cisco Secure Email

Enterprise email security with advanced malware and phishing protection.

FortiMail
FortiMail

Fortinet email security appliance with anti-spam and encryption.

Trend Micro Email Security
Trend Micro Email Security

Cloud-based email security with AI-powered threat detection.

Sophos Email
Sophos Email

Email security with anti-phishing, DLP, and encryption.

SpamExperts
SpamExperts

Email filtering service for inbound and outbound spam protection.

Hornetsecurity
Hornetsecurity

Cloud email security with compliance and backup features.

FireEye Email Security
FireEye Email Security

Advanced email threat protection against targeted attacks.

Classification

Three Protection Levels

Every email validation returns a protection_level so you can instantly segment your prospects.

None

No Protection

No dedicated email security gateway detected. No strict DMARC enforcement.

  • Standard spam filters only
  • Best deliverability for cold outreach
  • Prioritize these prospects
Basic

Basic Protection

Domain has SPF records and strict DMARC policy (quarantine or reject). No dedicated gateway.

  • SPF + strict DMARC enforced
  • Moderate outreach difficulty
  • Ensure proper authentication
Enterprise

Enterprise Gateway

A dedicated email security gateway is actively filtering inbound mail for this domain.

  • Aggressive content scanning
  • Cold email faces extra scrutiny
  • Deprioritize or personalize heavily
Process

How Detection Works

1

Enter an Email

Validate any email address through the dashboard, API, or bulk upload. Security detection runs automatically.

2

MX Record Analysis

MailRook inspects the domain's MX records and matches them against known patterns for 10 enterprise security providers.

3

Gateway + Level Returned

Get the specific gateways detected and overall protection level (none, basic, or enterprise) in every response.

API

Built Into Every Validation

The email_security and protection_level fields are included in every API response — no extra cost or configuration. 

{
  "email": "[email protected]",
  "status": "valid",
  "deliverable": true,
  ...
  "email_security": ["proofpoint"],
  "protection_level": "enterprise"
}
View full API documentation →
Use Cases

How Teams Use SEG Detection Data

Cold Outreach Prioritization

Sort your prospect list by protection level. Send to unprotected inboxes first for maximum reply rates. Save enterprise-protected contacts for warmer, more personalized sequences.

Domain Risk Assessment

Evaluate prospect domains before adding them to outreach sequences. Enterprise-protected domains need a different approach — know this before wasting credits.

Deliverability Optimization

Adjust your email content and sending strategy based on the recipient's protection level. Cleaner copy, fewer links, and proper authentication matter more for enterprise gateways.

Bulk List Segmentation

Upload your entire prospect list and export segments by protection level. Build separate sequences for each tier — maximize ROI across your full pipeline.

Explore More Products

MailRook offers a complete suite of email validation and intelligence tools.

Email Verification

Verify single emails in real-time

Bulk Verification

Verify thousands of emails at once

List Cleaning

Remove invalid contacts at scale

Validation API

Integrate into your application
Questions?

Email Security Gateway Detection FAQs

A secure email gateway (SEG) is a dedicated email security system — like Proofpoint, Mimecast, or Barracuda — that sits between the internet and a company's mail server. SEGs aggressively scan and filter inbound email, including cold outreach. If your prospect's domain uses a SEG, your cold email faces content scanning, reputation checks, and behavioral analysis far beyond standard spam filters. Knowing this before you send lets you adapt your approach or prioritize unprotected inboxes.
MailRook automatically checks for you. When you validate any email address, MailRook inspects the domain's MX records and identifies which secure email gateway is protecting it. The result includes the specific provider name (e.g., "proofpoint") and an overall protection level. You can check single emails via the dashboard, bulk lists via CSV upload, or programmatically via the API. No manual MX lookups needed.
MailRook detects 10 enterprise secure email gateways: Proofpoint, Mimecast, Barracuda, Cisco Email Security, FortiMail (Fortinet), Trend Micro Email Security, Sophos Email, SpamExperts, Hornetsecurity, and FireEye Email Security. We continuously add new providers as the market evolves.
Not necessarily. SEG-protected leads are harder to reach with cold email, but they're often high-value enterprise prospects. The best approach is to segment your list: send to unprotected inboxes first for volume, and use warmer, more personalized sequences for SEG-protected contacts. Some teams also throttle volume, avoid link-heavy content, or use longer warmup periods for SEG-protected domains.
SEG detection helps you avoid blind sending to heavily filtered inboxes, which hurts your sender reputation and wastes outreach volume. By routing unprotected leads into high-volume sequences and SEG-protected leads into personalized sequences, you get better inbox placement, higher reply rates, and protect your domain reputation. It's the same approach tools like Instantly recommend for SEG-aware campaigns.
Yes. Email security gateway detection is included in every email validation — including the free tier's 100 daily checks. There is no extra cost or configuration. The email_security and protection_level fields appear in every API response automatically.

Check Email Security Gateways Before You Send

Start with 100 free SEG checks per day. Know which prospects are behind Proofpoint, Mimecast, or Barracuda before your cold email hits their filters.

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