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Blocking Emails Containing PAN or Aadhaar Numbers in Google Workspace (Inbound & Outbound) – Bison Knowledgebase

Blocking Emails Containing PAN or Aadhaar Numbers in Google Workspace (Inbound & Outbound)

📅 01 Jan 2026 📂 General 👁 15 views

Indian organizations handling financial, identity, HR, or compliance-sensitive data must prevent accidental or unauthorized sharing of PAN (Permanent Account Number) and Aadhaar Number through email. Email is inherently insecure, and misuse of these identifiers can lead to legal violations, data breaches, and regulatory penalties.

This Knowledge Base article explains how to block incoming and/or outgoing emails that contain PAN or Aadhaar numbers—either in the email body or attachments—using Google Workspace, with clear steps, limitations, and best practices.

Is This Possible in Google Workspace?

Short Answer

✅ Yes, it is possible
⚠️ The level of control depends on your Google Workspace edition

Capability by Google Workspace Edition

EditionEmail BodyAttachmentsOCR (Scanned PDFs/Images)
Business Starter✅ Regex-based❌ Limited❌
Business Standard✅ Regex-based⚠️ Limited❌
Business Plus✅ DLP✅ DLP❌
Enterprise✅ Advanced DLP✅ Advanced DLP✅ OCR

Recommendation: For robust protection (including attachments), Business Plus or Enterprise is strongly advised.

Technical Explanation

Google Workspace provides two technical mechanisms to control sensitive data in Gmail:

1) Content Compliance Rules (Regex-Based)

  • Available in all editions

  • Uses pattern matching (regular expressions)

  • Scans:

    • Email subject

    • Email body

  • Cannot reliably scan attachment content

2) Data Loss Prevention (DLP) Rules

  • Available in Business Plus & Enterprise

  • Uses built-in detectors for:

    • India PAN Number

    • India Aadhaar Number

  • Scans:

    • Email body

    • Attachments (PDF, DOCX, XLSX, TXT)

    • Images & scanned documents (OCR – Enterprise only)

  • Lower false positives due to validation logic

PAN and Aadhaar Detection Logic

PAN Number Format

ABCDE1234F

  • 5 uppercase letters

  • 4 digits

  • 1 uppercase letter

Aadhaar Number Format

1234 5678 9123
or
123456789123

  • 12 digits

  • Starts from 2–9 (as per UIDAI rules)

Use Cases

Typical Scenarios

  • Accounting and CA firms

  • HR departments handling KYC documents

  • Financial services and NBFCs

  • Loan processing teams

  • MSPs managing compliance for clients

Policy Objectives

  • Block outgoing emails with PAN/Aadhaar

  • Quarantine or reject incoming emails with PAN/Aadhaar

  • Alert compliance or IT administrators

  • Maintain audit logs for investigations

Method 1: Content Compliance Rules (All Editions)

Suitable When

  • You are on Business Starter

  • PAN/Aadhaar appears mainly in email body

  • Attachments are handled via other secure channels

Step-by-Step Configuration

Step 1: Open Gmail Compliance

Admin Console → Apps → Google Workspace → Gmail → Compliance

Step 2: Create a Content Compliance Rule

  • Click Add rule

  • Rule type: Content compliance

Step 3: Define Message Scope

Choose one or more:

  • Outbound

  • Inbound

  • Internal

Example:

Outbound → All users

Step 4: Add PAN Regex

\b[A-Z]{5}[0-9]{4}[A-Z]\b

Step 5: Add Aadhaar Regex

\b[2-9]{1}[0-9]{3}\s?[0-9]{4}\s?[0-9]{4}\b

Step 6: Define Actions

Recommended:

  • Reject message

  • Quarantine

  • Notify admin

Example:

If matched → Reject message + Notify compliance@company.com

Step 7: Save and Enforce

  • Rule becomes active in 15–30 minutes

Method 2: Data Loss Prevention (DLP) Rules (Recommended)

Available in Business Plus and Enterprise

Step-by-Step Configuration

Step 1: Open DLP Rules

Admin Console → Security → Data protection → Rules

Step 2: Create a New Rule

  • Data source: Gmail

  • Direction:

    • Outbound (recommended)

    • Inbound (optional)

    • Internal (optional)

Step 3: Select Built-in Detectors

Choose:

  • India PAN Number

  • India Aadhaar Number

These detectors:

  • Validate structure

  • Reduce false positives

  • Work inside attachments

Step 4: Set Detection Threshold

Example:

Trigger if ≥ 1 PAN OR Aadhaar detected

Step 5: Configure Actions

Recommended:

  • Block message

  • Quarantine

  • Alert admin

  • Log event for audit

Step 6: Enable Attachment & OCR Scanning (Enterprise)

  • Scan attachments

  • Inspect PDFs, Office files

  • Enable OCR for scanned images

Example Policy Logic

IF (PAN detected OR Aadhaar detected)
AND Direction = Outbound
THEN
  Block email
  Notify admin
  Log DLP event

Commands / Validation Examples

Test PAN in Email Body

ABCDE1234F

Expected result: Email blocked or quarantined

Test Aadhaar in PDF Attachment

1234 5678 9123

Expected result:

  • Business Starter: ❌ May pass

  • Business Plus / Enterprise: ✅ Blocked

Common Issues & Fixes

Issue: False Positives

Fix

  • Use built-in DLP detectors instead of regex

  • Increase confidence thresholds

  • Exclude trusted internal domains if required

Issue: Attachments Not Blocked

Fix

  • Upgrade to Business Plus or Enterprise

  • Enable attachment inspection in DLP

Issue: Password-Protected ZIP Files

Fix

  • Block encrypted attachments

  • Enforce secure document portals instead of email

Security & Legal Considerations (India)

  • Aadhaar Act restricts transmission of Aadhaar numbers

  • PAN is protected under IT Act and privacy guidelines

  • Email is not considered a secure KYC channel

  • DLP logs support audits and regulatory reviews

Best Practices

  • Always block outbound PAN/Aadhaar emails

  • Use secure portals or encrypted systems for document exchange

  • Combine Content Compliance + DLP

  • Enable admin alerts and audit logging

  • Train users with warning banners

  • Review DLP incidents monthly

  • Maintain an exception approval workflow

Limitations

LimitationNotes
Business StarterNo attachment content scanning
Encrypted filesContent cannot be inspected
ScreenshotsRequire OCR (Enterprise only)
External forwardingNeeds separate routing controls

Conclusion

Yes—Google Workspace can effectively block incoming and/or outgoing emails containing PAN or Aadhaar numbers, provided the correct controls are implemented.

  • Business Starter: Regex-based blocking (basic protection)

  • Business Plus / Enterprise: Full DLP with attachment and OCR scanning

  • Best approach: Enforce outbound blocking, audit inbound flow, and use secure alternatives to email

This control is strongly recommended for Indian organizations handling sensitive identity data.


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