Welcome to our service.
'\n});\n\nconsole.log(`Email sent: ${result.messageId}`);\n```\n\n## Core Concepts\n\n### 1. Multi-Provider Email Sending\n\n```typescript\n// Configure multiple providers\nconst service = new EmailService({\n providers: [\n {\n type: 'sendgrid',\n apiKey: process.env.SENDGRID_API_KEY\n },\n {\n type: 'mailgun',\n apiKey: process.env.MAILGUN_API_KEY,\n domain: 'mg.yourdomain.com'\n },\n {\n type: 'ses',\n region: 'us-east-1',\n apiKey: process.env.AWS_ACCESS_KEY,\n secretKey: process.env.AWS_SECRET_KEY\n },\n {\n type: 'smtp',\n smtp: {\n host: 'smtp.gmail.com',\n port: 587,\n secure: false,\n auth: {\n user: process.env.SMTP_USER,\n pass: process.env.SMTP_PASS\n }\n }\n }\n ],\n defaultProvider: 'sendgrid',\n database: { type: 'sqlite', database: './email.db' }\n});\n\n// Send via specific provider\nawait service.send({\n from: 'noreply@yourdomain.com',\n to: ['user@example.com'],\n subject: 'Test',\n html: 'Test
',\n provider: 'mailgun' // Override default\n});\n```\n\n### 2. Template Management\n\n```typescript\n// Create template\nconst template = await service.createTemplate({\n name: 'welcome-email',\n subject: 'Welcome {{name}}!',\n html: `\nWelcome to {{company}}!
\nYour account email is: {{email}}
\n `,\n text: 'Hello {{name}}, welcome to {{company}}!'\n});\n\n// Send using template\nawait service.send({\n from: 'noreply@yourdomain.com',\n to: ['user@example.com'],\n templateId: template.id,\n templateData: {\n name: 'John Doe',\n company: 'Acme Corp',\n email: 'john@example.com'\n }\n});\n\n// Update template\nawait service.updateTemplate(template.id, {\n subject: 'Welcome to {{company}}, {{name}}!',\n html: 'This will retry up to 3 times if it fails
'\n});\n\nconsole.log(result.retryCount); // Number of retries that occurred\n```\n\n**Retry Features**:\n- ✅ Exponential backoff with jitter to avoid thundering herd\n- ✅ Configurable max retries and delays\n- ✅ Automatic retry on transient failures\n- ✅ Retry metrics tracking (attempts, successes, failures)\n- ✅ Integrates with `@bernierllc/retry-policy`, `retry-state`, and `retry-metrics`\n\n**Validation Features**:\n- ✅ Syntax validation (RFC 5322 compliance)\n- ✅ Domain validation (MX record checks when strict mode enabled)\n- ✅ Disposable email detection\n- ✅ Multiple recipient validation\n- ✅ Integrates with `@bernierllc/email-validator`\n\n### 5. Delivery Tracking\n\n```typescript\n// Send email\nconst result = await service.send({\n from: 'noreply@yourdomain.com',\n to: ['user@example.com'],\n subject: 'Order Confirmation',\n html: 'This is your reminder
',\n scheduledAt: new Date(Date.now() + 24 * 60 * 60 * 1000) // 24 hours\n});\n\n// Send with priority\nawait service.send({\n from: 'alerts@yourdomain.com',\n to: ['admin@yourdomain.com'],\n subject: 'URGENT: System Alert',\n html: 'Critical alert
',\n priority: 'high' // high, normal, low\n});\n```\n\n### 6. Bulk Sending\n\n```typescript\nconst results = await service.sendBulk([\n {\n from: 'noreply@yourdomain.com',\n to: ['user1@example.com'],\n subject: 'Personalized for User 1',\n html: 'Hello User 1
'\n },\n {\n from: 'noreply@yourdomain.com',\n to: ['user2@example.com'],\n subject: 'Personalized for User 2',\n html: 'Hello User 2
'\n }\n]);\n\nresults.forEach((result, index) => {\n console.log(`Email ${index + 1}: ${result.success ? 'sent' : 'failed'}`);\n});\n```\n\n### 7. Webhook Handling\n\n```typescript\n// Register webhook handler\nservice.registerWebhookHandler('delivered', async (event) => {\n console.log(`Email ${event.messageId} was delivered`);\n // Update your database, trigger workflows, etc.\n});\n\nservice.registerWebhookHandler('opened', async (event) => {\n console.log(`Email ${event.messageId} was opened`);\n // Track user engagement\n});\n\nservice.registerWebhookHandler('clicked', async (event) => {\n console.log(`Link clicked in ${event.messageId}`);\n // Track click-through rates\n});\n\nservice.registerWebhookHandler('bounced', async (event) => {\n console.log(`Email ${event.messageId} bounced`);\n // Update subscriber status\n await service.unsubscribe(event.data.email);\n});\n\n// Process webhook from provider\nawait service.handleWebhook({\n provider: 'sendgrid',\n event: 'delivered',\n messageId: 'msg_123',\n timestamp: new Date(),\n data: { /* provider-specific data */ }\n});\n```\n\n## API Reference\n\n### EmailService\n\n#### Constructor\n\n```typescript\nnew EmailService(config: EmailServiceConfig)\n```\n\n**Configuration:**\n\n```typescript\ninterface EmailServiceConfig {\n providers: ProviderConfig[];\n defaultProvider?: EmailProvider;\n database: DatabaseConfig;\n queue?: QueueOptions;\n templates?: {\n cacheEnabled?: boolean;\n cacheTTL?: number;\n };\n tracking?: {\n enabled?: boolean;\n domain?: string;\n };\n compliance?: {\n unsubscribeLink?: boolean;\n footerRequired?: boolean;\n };\n}\n\ninterface ProviderConfig {\n type: 'sendgrid' | 'mailgun' | 'ses' | 'smtp';\n apiKey?: string;\n domain?: string;\n region?: string;\n smtp?: SMTPConfig;\n rateLimit?: RateLimitConfig;\n}\n```\n\n#### Methods\n\n##### Email Sending\n\n- `send(request: EmailRequest): Promise