Email Worker

The Email Worker is a production-ready worker that sends emails via SMTP. It supports multiple SMTP configurations, HTML and plain text emails, attachments, CC/BCC, and all standard email features.

Features

• Multiple SMTP configurations (Default, Marketing, Transactional, etc.)
• HTML and plain text email body
• File attachments (regular and inline for HTML)
• CC and BCC recipients
• Custom email headers
• Email priority levels (High, Normal, Low)
• Read and delivery receipts
• Reply-To address
• Automatic retry for transient errors
• Permanent failure detection (no retry for invalid recipients)

Use Cases

Scenario	Example
Transactional Emails	Order confirmations, password resets
Notifications	Alert emails, status updates
Marketing Campaigns	Scheduled newsletter sends
Reports	Daily/weekly report delivery with attachments
System Alerts	Error notifications, monitoring alerts
Welcome Emails	New user onboarding sequences

Security Model

Like the SQL Worker, SMTP credentials are stored securely in the worker configuration, not in job data.

Worker (appsettings.json)

EmailConfig
└─ SmtpConfigs
   └─ Default
      ├─ Host: smtp.gmail.com
      ├─ Username: ********
      └─ Password: ********

(secrets stay here)

Only the configuration name (alias) is referenced in job data:

{
  "configName": "Default",
  "to": ["[email protected]"],
  "subject": "Welcome!",
  "body": "<h1>Hello!</h1>"
}

This design ensures that sensitive credentials never leave the worker environment.

Worker Configuration

Configure SMTP servers in the worker's appsettings.json:

{
  "EmailConfig": {
    "DefaultConfigName": "Default",
    "SmtpConfigs": {
      "Default": {
        "Host": "smtp.gmail.com",
        "Port": 587,
        "Username": "[email protected]",
        "Password": "your-app-password",
        "UseSsl": true,
        "DefaultFromEmail": "[email protected]",
        "DefaultFromName": "Your Company",
        "TimeoutSeconds": 30,
        "IgnoreCertificateErrors": false
      },
      "Marketing": {
        "Host": "smtp.sendgrid.net",
        "Port": 587,
        "Username": "apikey",
        "Password": "your-sendgrid-api-key",
        "UseSsl": true,
        "DefaultFromEmail": "[email protected]",
        "DefaultFromName": "Your Company Marketing",
        "TimeoutSeconds": 30
      },
      "Transactional": {
        "Host": "smtp.mailgun.org",
        "Port": 587,
        "Username": "[email protected]",
        "Password": "your-mailgun-password",
        "UseSsl": true,
        "DefaultFromEmail": "[email protected]",
        "DefaultFromName": "Your Company"
      }
    }
  }
}

SMTP Configuration Properties

Property	Type	Required	Default	Description
Host	string	✓	-	SMTP server hostname
Port	number	-	587	SMTP port (25, 465, or 587)
Username	string	-	-	SMTP authentication username
Password	string	-	-	SMTP authentication password
UseSsl	boolean	-	true	Enable SSL/TLS encryption
DefaultFromEmail	string	✓	-	Default sender email address
DefaultFromName	string	-	-	Default sender display name
TimeoutSeconds	number	-	30	Connection timeout
IgnoreCertificateErrors	boolean	-	false	Skip SSL certificate validation

Job Data Schema

When creating an email job, provide the email details through Job Data JSON:

{
  "configName": "Default",
  "to": ["[email protected]"],
  "cc": ["[email protected]"],
  "bcc": ["[email protected]"],
  "subject": "Monthly Report - January 2024",
  "body": "<h1>Monthly Report</h1><p>Please find attached...</p>",
  "isHtml": true,
  "fromEmail": "[email protected]",
  "fromName": "Reports System",
  "replyTo": "[email protected]",
  "priority": "High",
  "attachments": [
    {
      "fileName": "report.pdf",
      "contentBase64": "JVBERi0xLjQK...",
      "contentType": "application/pdf"
    }
  ],
  "requestReadReceipt": false,
  "requestDeliveryReceipt": true
}

Configuration Reference

Main Properties

Property	Type	Required	Default	Description
configName	string	-	Default config	SMTP configuration alias
to	array	✓	-	Recipient email addresses
cc	array	-	-	CC recipients
bcc	array	-	-	BCC recipients (hidden)
subject	string	✓	-	Email subject line
body	string	✓	-	Email body content
isHtml	boolean	-	false	Whether body is HTML
fromEmail	string	-	From config	Override sender email
fromName	string	-	From config	Override sender name
replyTo	string	-	-	Reply-To address
priority	enum	-	Normal	Priority: Low, Normal, High
attachments	array	-	-	File attachments
customHeaders	object	-	-	Custom email headers
requestReadReceipt	boolean	-	false	Request read receipt
requestDeliveryReceipt	boolean	-	false	Request delivery receipt

Attachment Properties

Property	Type	Required	Description
fileName	string	✓	File name with extension
contentBase64	string	✓	Base64-encoded file content
contentType	string	-	MIME type (auto-detected if omitted)
isInline	boolean	-	Inline attachment for HTML
contentId	string	-	Content ID for inline (use as cid:value)

Deployment

docker run -d --name milvaion-email-worker --network milvaion_milvaion-network milvasoft/milvaion-email-worker:latest

Docker Compose

services:
  email-worker:
    image: milvasoft/milvaion-email-worker:latest
    environment:
      - Worker__WorkerId=email-worker-01
      - Worker__RabbitMQ__Host=rabbitmq
      - Worker__Redis__ConnectionString=redis:6379
      - EmailConfig__DefaultConfigName=Default
      - EmailConfig__SmtpConfigs__Default__Host=smtp.gmail.com
      - EmailConfig__SmtpConfigs__Default__Port=587
      - EmailConfig__SmtpConfigs__Default__Username=${SMTP_USERNAME}
      - EmailConfig__SmtpConfigs__Default__Password=${SMTP_PASSWORD}
      - EmailConfig__SmtpConfigs__Default__UseSsl=true
      - EmailConfig__SmtpConfigs__Default__DefaultFromEmail=noreply@yourcompany.com
      - EmailConfig__SmtpConfigs__Default__DefaultFromName=Your Company
    depends_on:
      - rabbitmq
      - redis
    restart: unless-stopped

Environment Variables

All SMTP configurations can be overridden via environment variables:

# Default SMTP Configuration
EmailConfig__SmtpConfigs__Default__Host=smtp.gmail.com
EmailConfig__SmtpConfigs__Default__Port=587
EmailConfig__SmtpConfigs__Default__Username=[email protected]
EmailConfig__SmtpConfigs__Default__Password=your-app-password
EmailConfig__SmtpConfigs__Default__UseSsl=true
EmailConfig__SmtpConfigs__Default__DefaultFromEmail=[email protected]
EmailConfig__SmtpConfigs__Default__DefaultFromName=Your Company

# Marketing SMTP Configuration
EmailConfig__SmtpConfigs__Marketing__Host=smtp.sendgrid.net
EmailConfig__SmtpConfigs__Marketing__Port=587
EmailConfig__SmtpConfigs__Marketing__Username=apikey
EmailConfig__SmtpConfigs__Marketing__Password=your-sendgrid-api-key

# Timeout and SSL Settings
EmailConfig__SmtpConfigs__Default__TimeoutSeconds=30
EmailConfig__SmtpConfigs__Default__IgnoreCertificateErrors=false

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: email-worker
spec:
  replicas: 2
  selector:
    matchLabels:
      app: email-worker
  template:
    metadata:
      labels:
        app: email-worker
    spec:
      containers:
        - name: email-worker
          image: milvasoft/milvaion-email-worker:latest
          env:
            - name: Worker__WorkerId
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
            - name: Worker__RabbitMQ__Host
              value: rabbitmq-service
            - name: Worker__Redis__ConnectionString
              value: redis-service:6379
            - name: EmailConfig__SmtpConfigs__Default__Password
              valueFrom:
                secretKeyRef:
                  name: email-secrets
                  key: smtp-password
          envFrom:
            - configMapRef:
                name: email-worker-config
---
apiVersion: v1
kind: Secret
metadata:
  name: email-secrets
type: Opaque
stringData:
  smtp-password: your-smtp-password
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: email-worker-config
data:
  EmailConfig__SmtpConfigs__Default__Host: smtp.gmail.com
  EmailConfig__SmtpConfigs__Default__Port: "587"
  EmailConfig__SmtpConfigs__Default__Username: your-[email protected]
  EmailConfig__SmtpConfigs__Default__UseSsl: "true"
  EmailConfig__SmtpConfigs__Default__DefaultFromEmail: [email protected]
  EmailConfig__SmtpConfigs__Default__DefaultFromName: Your Company

Scaling Considerations

Factor	Recommendation
Replicas	2-4 workers for high-volume email sending
Rate Limiting	Respect SMTP provider limits (Gmail: 500/day, SendGrid: varies)
Retry Strategy	Built-in retry handles transient failures automatically
Memory	~256MB per worker (more if handling large attachments)

---

For custom workers, see Your First Worker and Implementing Jobs.