Improvement Plan for SmartMail

Current Code Analysis

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- EmailAddressValidator: Validates email addresses checking for validity, whether they are disposable or free
- Uses MX record checks to validate domains
- Has a domain map from external source that classifies domains as 'disposable' or 'freemail'
- Has placeholder 'reason' field in results that's not implemented ("todo")
- Fetches domain list from GitHub or falls back to local copy
- No validation of email format before DNS checks

- Smartmail: Email representation class
- Basic email structure with from, subject, body
- Supports file attachments via smartfile
- Uses mustache templates for subject and body
- Lacks recipient handling (to, cc, bcc)
- No method to send emails
- No HTML body support

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- Uses several @push.rocks packages:
- smartdns: For DNS lookups
- smartfile: For file handling/attachments
- smartmustache: For template processing
- smartpath: For path operations
- smartrequest: For HTTP requests

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- Basic tests for EmailAddressValidator
- Tests validation of regular, free, and disposable emails
- No tests for invalid email formats or edge cases
- Minimal test for Smartmail creation
- No tests for attachments, templates, or other features

Enhanced Improvement Plan

1. [x] Complete the EmailAddressValidator implementation
- [x] Implement proper reason messages for validation results
- [x] Add email format validation before DNS checks (RFC 5322 compliance)
- [x] Add local part validation (check for illegal characters, proper format)
- [x] Improve domain validation (check syntax before DNS lookup)
- [x] Add email normalization (handle case sensitivity, plus addressing)
- [x] Implement caching mechanism for DNS lookups to improve performance
- [x] Add option to disable online domain list fetching

2. [x] Enhance the Smartmail class
- [x] Add support for multiple recipients (to, cc, bcc arrays)
- [x] Add email preparing capabilities via MIME format
- [x] Support HTML email bodies with plain text fallback
- [x] Add reply-to and headers support
- [x] Implement method to convert to standard email formats (MIME)
- [x] Add email priority and importance flags
- [x] Add validation of email addresses used in from/to/cc/bcc

3. [x] Improve testing
- [x] Add tests for email format validation (valid/invalid formats)
- [x] Test domain validation edge cases (non-existent domains, etc.)
- [x] Add tests for attachment handling
- [x] Test template processing with different data structures
- [x] Add tests for HTML emails and conversion
- [x] Test recipient handling with multiple addresses

4. [x] Performance & security improvements
- [x] Optimize domain list handling
- [x] Implement intelligent caching strategy for validation results
- [x] Add configuration options for external service calls
- [x] Ensure secure handling of email data and attachments

5. [x] Documentation improvements
- [x] Update README with comprehensive examples
- [x] Add detailed API documentation with JSDoc
- [x] Document all configuration options
- [x] Add usage examples for common scenarios
- [x] Document security considerations
- [x] Add TypeScript type documentation

6. [ ] Advanced features
- [ ] DKIM/SPF validation support
- [ ] Implement email address suggestions for typos
- [ ] Add disposable email detection improvements
- [ ] Support for internationalized email addresses (IDN)
- [ ] Email address reputation checking
- [ ] Add email deliverability scoring
- [ ] Implement bounce address validation

7. [x] Code quality
- [x] Add more TypeScript interfaces for clearer API definitions
- [x] Improve error handling with specific error types
- [x] Add configuration options via constructor
- [x] Make domain list updates configurable
- [x] Improve code organization with better separation of concerns