PRD: Email System

Generated: 2025-07-23 00:00 UTC
Status: Complete
Verified:

Executive Summary

This PRD defines the email-based document conversion system that allows users to convert documents by simply sending them as email attachments. The system provides a frictionless conversion experience for non-technical users, automated processing workflows, and intelligent delivery mechanisms while maintaining security and preventing abuse.

Key Objectives

Enable document conversion via email for non-technical users
Provide automated attachment processing and conversion
Implement intelligent result delivery (reply, links, or cloud storage)
Ensure email security and spam prevention
Support bulk conversions and email automation workflows

User Stories

As a Business User

I want to email documents for conversion without using APIs
I want to receive converted files directly in my inbox
I want to convert multiple attachments in one email
I want simple instructions in the reply

As an Office Worker

I want to forward emails with attachments for conversion
I want to specify conversion options in the email subject
I want to share conversion results with colleagues
I want to save results to my cloud storage

As a System Administrator

I want to set up automated email workflows
I want to monitor email conversion usage
I want to configure security policies
I want to prevent email abuse

As a Mobile User

I want to convert documents from my phone
I want mobile-friendly result formats
I want download links that work on mobile
I want compressed results for data savings

Functional Requirements

Email Processing System

1. Email Addresses & Routing

Conversion Addresses:

convert@docconverter.com - Auto-detect format
xlsx@docconverter.com - Excel conversions
pdf@docconverter.com - PDF conversions
docx@docconverter.com - Word conversions
ppt@docconverter.com - PowerPoint conversions

Routing Rules:

graph LR A[Incoming Email] --> B{Address Parser} B -->|convert@| C[Auto-Detect] B -->|xlsx@| D[Excel Handler] B -->|pdf@| E[PDF Handler] B -->|docx@| F[Word Handler] C --> G[Format Detection] G --> D G --> E G --> F

2. Subject Line Commands

Format: [Action] [Options] | Original Subject

Examples:

Convert to JSON - Basic conversion
Convert to Markdown | Meeting Notes
XLSX to JSON sheets=1,3 | Sales Report
PDF OCR=true | Scanned Invoice
BATCH | Multiple Documents

Supported Commands:

to=format - Output format
sheets=1,2,3 - Specific sheets
pages=1-10 - Page range
ocr=true - Enable OCR
compress=true - Compress results
password=**** - Document password

3. Attachment Processing

Supported Attachments:

Single file conversion
Multiple file batch processing
Nested attachments (forwarded emails)
Compressed archives (ZIP)
Cloud storage links

Size Limits:

Free users: 10MB per email
Paid users: 50MB per email
Enterprise: 200MB per email
Maximum 20 attachments per email

4. Format Detection

{
  "detection_rules": {
    "excel": [".xlsx", ".xls", ".xlsm", ".xlsb"],
    "pdf": [".pdf"],
    "word": [".docx", ".doc", ".docm"],
    "powerpoint": [".pptx", ".ppt", ".pptm"],
    "auto_detect": {
      "mime_types": true,
      "file_signatures": true,
      "extension_fallback": true
    }
  }
}

Email Response System

1. Reply Formats

Standard Reply:

Subject: Re: [CONVERTED] Sales Report

Hello [Name],

Your document conversion is complete!

Converted Files:
✓ sales_report.xlsx → sales_report.json (245 KB)
✓ summary.pdf → summary.md (12 KB)

Results are attached to this email.

Conversion Details:
- Processing time: 3.2 seconds
- Format: Excel to JSON
- Sheets processed: All

Download Links (expire in 7 days):
- https://dl.converter.com/abc123/sales_report.json
- https://dl.converter.com/def456/summary.md

---
Document Converter Service
Need help? Reply with "HELP"

2. Delivery Options

Attachment Delivery:

Files < 10MB: Direct attachment
Files > 10MB: Download links
Multiple files: ZIP archive
Option to force links only

Cloud Storage Integration:

Google Drive upload
Dropbox integration
OneDrive support
Box.com integration
Custom S3 buckets

3. Error Handling

Error Response Template:

Subject: Re: [FAILED] Document Conversion

Hello [Name],

We couldn't convert your document.

Error: Unsupported file format
File: report.xyz

Supported formats:
- Excel: .xlsx, .xls
- PDF: .pdf
- Word: .docx, .doc
- PowerPoint: .pptx, .ppt

Please try again with a supported format.

---
Need help? Visit converter.com/help

Advanced Email Features

1. Email Templates

Custom Templates:

Branded email designs
Company logos and colors
Custom footer text
Localized content
HTML and plain text versions

2. Mailing List Support

Bulk Processing:

Distribution list handling
Batch result delivery
Progress notifications
Summary reports

Example:

To: weekly-reports@company.com
Subject: BATCH Convert to PDF | Weekly Reports

Attached: 25 Excel files

Results delivered to each recipient individually.

3. Email Automation

Webhook Triggers:

{
  "email_received": {
    "from": "user@company.com",
    "subject": "Daily Report",
    "attachments": ["report.xlsx"],
    "webhook_url": "https://company.com/process"
  }
}

Scheduled Processing:

Daily report conversions
Weekly batch processing
Monthly archive creation
Automated workflows

4. Reply Commands

Interactive Commands:

HELP - Get help information
STATUS job-123 - Check conversion status
RESEND job-123 - Resend results
DELETE job-123 - Delete stored results
UPGRADE - Upgrade account info

Security & Anti-Abuse

1. Sender Verification

SPF/DKIM/DMARC:

Strict sender validation
Domain whitelist/blacklist
Reply-to verification
Sender reputation scoring

2. Rate Limiting

Email Limits:

Free: 10 emails/day
Paid: 100 emails/day
Enterprise: Unlimited
Per-sender throttling

3. Spam Prevention

graph TD A[Email Received] --> B{Spam Check} B -->|Pass| C{Rate Limit} B -->|Fail| D[Reject] C -->|OK| E{Virus Scan} C -->|Exceeded| F[Queue/Reject] E -->|Clean| G[Process] E -->|Infected| H[Quarantine]

4. Content Filtering

Virus scanning
Malware detection
Phishing prevention
Suspicious attachment blocking

Non-Functional Requirements

Performance Requirements

Email processing latency < 30 seconds
Attachment extraction < 5 seconds
Conversion queuing < 1 second
Reply delivery < 2 minutes

Scalability Requirements

100K+ emails/day capacity
Concurrent processing
Auto-scaling workers
Geographic distribution

Reliability Requirements

Email delivery rate > 99%
No lost attachments
Retry failed deliveries
Dead letter queue handling

Technical Specifications

Email Infrastructure

1. Inbound Email Processing

email_pipeline:
  mx_records:
    - priority: 10
      server: mx1.converter.com
    - priority: 20
      server: mx2.converter.com
  
  processing:
    - spam_filter: SpamAssassin
    - virus_scan: ClamAV
    - parser: Custom MIME parser
    - queue: SQS/Pub-Sub

2. Email Parser Architecture

class EmailProcessor:
    def process(self, email):
        # Extract metadata
        sender = self.verify_sender(email)
        subject = self.parse_subject(email)
        
        # Extract attachments
        attachments = self.extract_attachments(email)
        
        # Process conversions
        for attachment in attachments:
            job = self.create_conversion_job(
                attachment,
                subject.options
            )
            self.queue_job(job)
        
        # Send response
        self.send_reply(sender, jobs)

3. Delivery System

SMTP Configuration:

SendGrid/AWS SES for delivery
Dedicated IP addresses
Warm-up procedures
Bounce handling

Storage & Retention

1. Email Storage

Original emails: 30 days
Attachments: Processed immediately
Results: Based on user tier
Logs: 90 days

2. Data Flow

sequenceDiagram participant User participant MX participant Parser participant Converter participant Storage participant SMTP User->>MX: Send email MX->>Parser: Queue email Parser->>Converter: Extract & convert Converter->>Storage: Store results Storage->>SMTP: Generate reply SMTP->>User: Deliver results

Success Metrics

Usage Metrics

Daily email conversions
Average attachments per email
Conversion success rate > 95%
Email delivery rate > 99%

Performance Metrics

Email to reply time < 3 minutes
Attachment processing < 30 seconds
Queue depth < 1000 emails
Error rate < 1%

User Satisfaction

Email bounce rate < 2%
Spam complaints < 0.1%
Support tickets < 5%
User retention > 80%

Dependencies

External Services

Email delivery service (SendGrid/SES)
Anti-spam service
Virus scanning
Cloud storage APIs

Internal Services

Conversion engine
User authentication
Billing system
Analytics platform

Timeline & Milestones

Phase 1: Basic Email (Months 1-2)

Inbound email processing
Single attachment conversion
Basic reply system
Error handling

Phase 2: Advanced Features (Months 2-3)

Multiple attachments
Subject line commands
Cloud storage integration
Custom templates

Phase 3: Automation (Months 3-4)

Mailing list support
Scheduled processing
Email workflows
API integration

Phase 4: Enterprise (Months 4-5)

Custom domains
Advanced security
Compliance features
White-label options

Risk Mitigation

Technical Risks

Email delivery issues: Multiple delivery providers
Spam classification: Proper authentication
Attachment corruption: Integrity checking

Security Risks

Malware distribution: Comprehensive scanning
Phishing attempts: Sender verification
Data leakage: Encryption and access controls

Business Risks

Abuse/spam: Rate limiting and monitoring
Support burden: Self-service help
Scaling costs: Efficient processing

Future Considerations

Enhanced Features

AI-powered format detection
Smart conversion suggestions
Email-based workflows
Voice note transcription

Integration Options

CRM email integration
Slack/Teams connectors
IFTTT/Zapier support
Email client plugins