dcrouter/test

DCRouter SMTP Test Suite

test/
├── readme.md                              # This file
├── helpers/
│   ├── server.loader.ts                  # SMTP server lifecycle management
│   ├── utils.ts                          # Common test utilities
│   └── smtp.client.ts                    # Test SMTP client utilities
└── suite/
    ├── smtpserver_commands/              # SMTP command tests (CMD)
    ├── smtpserver_connection/            # Connection management tests (CM)
    ├── smtpserver_edge-cases/            # Edge case tests (EDGE)
    ├── smtpserver_email-processing/      # Email processing tests (EP)
    ├── smtpserver_error-handling/        # Error handling tests (ERR)
    ├── smtpserver_performance/           # Performance tests (PERF)
    ├── smtpserver_reliability/           # Reliability tests (REL)
    ├── smtpserver_rfc-compliance/        # RFC compliance tests (RFC)
    └── smtpserver_security/              # Security tests (SEC)

Test ID Convention

All test files follow a strict naming convention: test.<category-id>.<description>.ts

Examples:

• test.cmd-01.ehlo-command.ts - EHLO command test
• test.cm-01.tls-connection.ts - TLS connection test
• test.sec-01.authentication.ts - Authentication test

Test Categories

1. Connection Management (CM)

Tests for validating SMTP connection handling, TLS support, and connection lifecycle management.

ID	Test Description	Priority	Implementation
CM-01	TLS Connection Test	High	suite/smtpserver_connection/test.cm-01.tls-connection.ts
CM-02	Multiple Simultaneous Connections	High	suite/smtpserver_connection/test.cm-02.multiple-connections.ts
CM-03	Connection Timeout	High	suite/smtpserver_connection/test.cm-03.connection-timeout.ts
CM-04	Connection Limits	Medium	suite/smtpserver_connection/test.cm-04.connection-limits.ts
CM-05	Connection Rejection	Medium	suite/smtpserver_connection/test.cm-05.connection-rejection.ts
CM-06	STARTTLS Connection Upgrade	High	suite/smtpserver_connection/test.cm-06.starttls-upgrade.ts
CM-07	Abrupt Client Disconnection	Medium	suite/smtpserver_connection/test.cm-07.abrupt-disconnection.ts
CM-08	TLS Version Compatibility	Medium	suite/smtpserver_connection/test.cm-08.tls-versions.ts
CM-09	TLS Cipher Configuration	Medium	suite/smtpserver_connection/test.cm-09.tls-ciphers.ts
CM-10	Plain Connection Test	Low	suite/smtpserver_connection/test.cm-10.plain-connection.ts
CM-11	TCP Keep-Alive Test	Low	suite/smtpserver_connection/test.cm-11.keepalive.ts

2. SMTP Commands (CMD)

Tests for validating proper SMTP protocol command implementation.

ID	Test Description	Priority	Implementation
CMD-01	EHLO Command	High	suite/smtpserver_commands/test.cmd-01.ehlo-command.ts
CMD-02	MAIL FROM Command	High	suite/smtpserver_commands/test.cmd-02.mail-from.ts
CMD-03	RCPT TO Command	High	suite/smtpserver_commands/test.cmd-03.rcpt-to.ts
CMD-04	DATA Command	High	suite/smtpserver_commands/test.cmd-04.data-command.ts
CMD-05	NOOP Command	Medium	suite/smtpserver_commands/test.cmd-05.noop-command.ts
CMD-06	RSET Command	Medium	suite/smtpserver_commands/test.cmd-06.rset-command.ts
CMD-07	VRFY Command	Low	suite/smtpserver_commands/test.cmd-07.vrfy-command.ts
CMD-08	EXPN Command	Low	suite/smtpserver_commands/test.cmd-08.expn-command.ts
CMD-09	SIZE Extension	Medium	suite/smtpserver_commands/test.cmd-09.size-extension.ts
CMD-10	HELP Command	Low	suite/smtpserver_commands/test.cmd-10.help-command.ts
CMD-11	Command Pipelining	Medium	suite/smtpserver_commands/test.cmd-11.command-pipelining.ts
CMD-12	HELO Command	Low	suite/smtpserver_commands/test.cmd-12.helo-command.ts
CMD-13	QUIT Command	High	suite/smtpserver_commands/test.cmd-13.quit-command.ts

3. Email Processing (EP)

Tests for validating email content handling, parsing, and delivery.

ID	Test Description	Priority	Implementation
EP-01	Basic Email Sending	High	suite/smtpserver_email-processing/test.ep-01.basic-email-sending.ts
EP-02	Invalid Email Address Handling	High	suite/smtpserver_email-processing/test.ep-02.invalid-email-addresses.ts
EP-03	Multiple Recipients	Medium	suite/smtpserver_email-processing/test.ep-03.multiple-recipients.ts
EP-04	Large Email Handling	High	suite/smtpserver_email-processing/test.ep-04.large-email.ts
EP-05	MIME Handling	High	suite/smtpserver_email-processing/test.ep-05.mime-handling.ts
EP-06	Attachment Handling	Medium	suite/smtpserver_email-processing/test.ep-06.attachment-handling.ts
EP-07	Special Character Handling	Medium	suite/smtpserver_email-processing/test.ep-07.special-character-handling.ts
EP-08	Email Routing	High	suite/smtpserver_email-processing/test.ep-08.email-routing.ts
EP-09	Delivery Status Notifications	Medium	suite/smtpserver_email-processing/test.ep-09.delivery-status-notifications.ts

4. Security (SEC)

Tests for validating security features and protections.

ID	Test Description	Priority	Implementation
SEC-01	Authentication	High	suite/smtpserver_security/test.sec-01.authentication.ts
SEC-02	Authorization	High	suite/smtpserver_security/test.sec-02.authorization.ts
SEC-03	DKIM Processing	High	suite/smtpserver_security/test.sec-03.dkim-processing.ts
SEC-04	SPF Checking	High	suite/smtpserver_security/test.sec-04.spf-checking.ts
SEC-05	DMARC Policy Enforcement	Medium	suite/smtpserver_security/test.sec-05.dmarc-policy.ts
SEC-06	IP Reputation Checking	High	suite/smtpserver_security/test.sec-06.ip-reputation.ts
SEC-07	Content Scanning	Medium	suite/smtpserver_security/test.sec-07.content-scanning.ts
SEC-08	Rate Limiting	High	suite/smtpserver_security/test.sec-08.rate-limiting.ts
SEC-09	TLS Certificate Validation	High	suite/smtpserver_security/test.sec-09.tls-certificate-validation.ts
SEC-10	Header Injection Prevention	High	suite/smtpserver_security/test.sec-10.header-injection-prevention.ts
SEC-11	Bounce Management	Medium	suite/smtpserver_security/test.sec-11.bounce-management.ts

5. Error Handling (ERR)

Tests for validating proper error handling and recovery.

ID	Test Description	Priority	Implementation
ERR-01	Syntax Error Handling	High	suite/smtpserver_error-handling/test.err-01.syntax-errors.ts
ERR-02	Invalid Sequence Handling	High	suite/smtpserver_error-handling/test.err-02.invalid-sequence.ts
ERR-03	Temporary Failure Handling	Medium	suite/smtpserver_error-handling/test.err-03.temporary-failures.ts
ERR-04	Permanent Failure Handling	Medium	suite/smtpserver_error-handling/test.err-04.permanent-failures.ts
ERR-05	Resource Exhaustion Handling	High	suite/smtpserver_error-handling/test.err-05.resource-exhaustion.ts
ERR-06	Malformed MIME Handling	Medium	suite/smtpserver_error-handling/test.err-06.malformed-mime.ts
ERR-07	Exception Handling	High	suite/smtpserver_error-handling/test.err-07.exception-handling.ts
ERR-08	Error Logging	Medium	suite/smtpserver_error-handling/test.err-08.error-logging.ts

6. Performance (PERF)

Tests for validating performance characteristics and benchmarks.

ID	Test Description	Priority	Implementation
PERF-01	Throughput Testing	Medium	suite/smtpserver_performance/test.perf-01.throughput.ts
PERF-02	Concurrency Testing	High	suite/smtpserver_performance/test.perf-02.concurrency.ts
PERF-03	CPU Utilization	Medium	suite/smtpserver_performance/test.perf-03.cpu-utilization.ts
PERF-04	Memory Usage	Medium	suite/smtpserver_performance/test.perf-04.memory-usage.ts
PERF-05	Connection Processing Time	Medium	suite/smtpserver_performance/test.perf-05.connection-processing-time.ts
PERF-06	Message Processing Time	Medium	suite/smtpserver_performance/test.perf-06.message-processing-time.ts
PERF-07	Resource Cleanup	High	suite/smtpserver_performance/test.perf-07.resource-cleanup.ts

7. Reliability (REL)

Tests for validating system reliability and stability.

ID	Test Description	Priority	Implementation
REL-01	Long-Running Operation	High	suite/smtpserver_reliability/test.rel-01.long-running-operation.ts
REL-02	Restart Recovery	High	suite/smtpserver_reliability/test.rel-02.restart-recovery.ts
REL-03	Resource Leak Detection	High	suite/smtpserver_reliability/test.rel-03.resource-leak-detection.ts
REL-04	Error Recovery	High	suite/smtpserver_reliability/test.rel-04.error-recovery.ts
REL-05	DNS Resolution Failure Handling	Medium	suite/smtpserver_reliability/test.rel-05.dns-resolution-failure.ts
REL-06	Network Interruption Handling	Medium	suite/smtpserver_reliability/test.rel-06.network-interruption.ts

8. Edge Cases (EDGE)

Tests for validating handling of unusual or extreme scenarios.

ID	Test Description	Priority	Implementation
EDGE-01	Very Large Email	Low	suite/smtpserver_edge-cases/test.edge-01.very-large-email.ts
EDGE-02	Very Small Email	Low	suite/smtpserver_edge-cases/test.edge-02.very-small-email.ts
EDGE-03	Invalid Character Handling	Medium	suite/smtpserver_edge-cases/test.edge-03.invalid-character-handling.ts
EDGE-04	Empty Commands	Low	suite/smtpserver_edge-cases/test.edge-04.empty-commands.ts
EDGE-05	Extremely Long Lines	Medium	suite/smtpserver_edge-cases/test.edge-05.extremely-long-lines.ts
EDGE-06	Extremely Long Headers	Medium	suite/smtpserver_edge-cases/test.edge-06.extremely-long-headers.ts
EDGE-07	Unusual MIME Types	Low	suite/smtpserver_edge-cases/test.edge-07.unusual-mime-types.ts
EDGE-08	Nested MIME Structures	Low	suite/smtpserver_edge-cases/test.edge-08.nested-mime-structures.ts

9. RFC Compliance (RFC)

Tests for validating compliance with SMTP-related RFCs.

ID	Test Description	Priority	Implementation
RFC-01	RFC 5321 Compliance	High	suite/smtpserver_rfc-compliance/test.rfc-01.rfc5321-compliance.ts
RFC-02	RFC 5322 Compliance	High	suite/smtpserver_rfc-compliance/test.rfc-02.rfc5322-compliance.ts
RFC-03	RFC 7208 SPF Compliance	Medium	suite/smtpserver_rfc-compliance/test.rfc-03.rfc7208-spf-compliance.ts
RFC-04	RFC 6376 DKIM Compliance	Medium	suite/smtpserver_rfc-compliance/test.rfc-04.rfc6376-dkim-compliance.ts
RFC-05	RFC 7489 DMARC Compliance	Medium	suite/smtpserver_rfc-compliance/test.rfc-05.rfc7489-dmarc-compliance.ts
RFC-06	RFC 8314 TLS Compliance	Medium	suite/smtpserver_rfc-compliance/test.rfc-06.rfc8314-tls-compliance.ts
RFC-07	RFC 3461 DSN Compliance	Low	suite/smtpserver_rfc-compliance/test.rfc-07.rfc3461-dsn-compliance.ts

SMTP Client Test Suite

The following test categories ensure our SMTP client is production-ready, RFC-compliant, and handles all real-world scenarios properly.

Client Test Organization

test/
└── suite/
    ├── smtpclient_connection/          # Client connection management tests (CCM)
    ├── smtpclient_commands/            # Client command execution tests (CCMD)
    ├── smtpclient_email-composition/   # Email composition tests (CEP)
    ├── smtpclient_security/            # Client security tests (CSEC)
    ├── smtpclient_error-handling/      # Client error handling tests (CERR)
    ├── smtpclient_performance/         # Client performance tests (CPERF)
    ├── smtpclient_reliability/         # Client reliability tests (CREL)
    ├── smtpclient_edge-cases/          # Client edge case tests (CEDGE)
    └── smtpclient_rfc-compliance/      # Client RFC compliance tests (CRFC)

10. Client Connection Management (CCM)

Tests for validating how the SMTP client establishes and manages connections to servers.

ID	Test Description	Priority	Implementation
CCM-01	Basic TCP Connection	High	suite/smtpclient_connection/test.ccm-01.basic-tcp-connection.ts
CCM-02	TLS Connection Establishment	High	suite/smtpclient_connection/test.ccm-02.tls-connection.ts
CCM-03	STARTTLS Upgrade	High	suite/smtpclient_connection/test.ccm-03.starttls-upgrade.ts
CCM-04	Connection Pooling	High	suite/smtpclient_connection/test.ccm-04.connection-pooling.ts
CCM-05	Connection Reuse	Medium	suite/smtpclient_connection/test.ccm-05.connection-reuse.ts
CCM-06	Connection Timeout Handling	High	suite/smtpclient_connection/test.ccm-06.connection-timeout.ts
CCM-07	Automatic Reconnection	High	suite/smtpclient_connection/test.ccm-07.automatic-reconnection.ts
CCM-08	DNS Resolution & MX Records	High	suite/smtpclient_connection/test.ccm-08.dns-mx-resolution.ts
CCM-09	IPv4/IPv6 Dual Stack Support	Medium	suite/smtpclient_connection/test.ccm-09.dual-stack-support.ts
CCM-10	Proxy Support (SOCKS/HTTP)	Low	suite/smtpclient_connection/test.ccm-10.proxy-support.ts
CCM-11	Keep-Alive Management	Medium	suite/smtpclient_connection/test.ccm-11.keepalive-management.ts

11. Client Command Execution (CCMD)

Tests for validating how the client sends SMTP commands and processes responses.

ID	Test Description	Priority	Implementation
CCMD-01	EHLO/HELO Command Sending	High	suite/smtpclient_commands/test.ccmd-01.ehlo-helo-sending.ts
CCMD-02	MAIL FROM Command with Parameters	High	suite/smtpclient_commands/test.ccmd-02.mail-from-parameters.ts
CCMD-03	RCPT TO Command with Multiple Recipients	High	suite/smtpclient_commands/test.ccmd-03.rcpt-to-multiple.ts
CCMD-04	DATA Command and Content Transmission	High	suite/smtpclient_commands/test.ccmd-04.data-transmission.ts
CCMD-05	AUTH Command (LOGIN, PLAIN, CRAM-MD5)	High	suite/smtpclient_commands/test.ccmd-05.auth-mechanisms.ts
CCMD-06	Command Pipelining	Medium	suite/smtpclient_commands/test.ccmd-06.command-pipelining.ts
CCMD-07	Response Code Parsing	High	suite/smtpclient_commands/test.ccmd-07.response-parsing.ts
CCMD-08	Extended Response Handling	Medium	suite/smtpclient_commands/test.ccmd-08.extended-responses.ts
CCMD-09	QUIT Command and Graceful Disconnect	High	suite/smtpclient_commands/test.ccmd-09.quit-disconnect.ts
CCMD-10	RSET Command Usage	Medium	suite/smtpclient_commands/test.ccmd-10.rset-usage.ts
CCMD-11	NOOP Keep-Alive	Low	suite/smtpclient_commands/test.ccmd-11.noop-keepalive.ts

12. Client Email Composition (CEP)

Tests for validating email composition, formatting, and encoding.

ID	Test Description	Priority	Implementation
CEP-01	Basic Email Headers	High	suite/smtpclient_email-composition/test.cep-01.basic-headers.ts
CEP-02	MIME Multipart Messages	High	suite/smtpclient_email-composition/test.cep-02.mime-multipart.ts
CEP-03	Attachment Encoding	High	suite/smtpclient_email-composition/test.cep-03.attachment-encoding.ts
CEP-04	UTF-8 and International Characters	High	suite/smtpclient_email-composition/test.cep-04.utf8-international.ts
CEP-05	Base64 and Quoted-Printable Encoding	Medium	suite/smtpclient_email-composition/test.cep-05.content-encoding.ts
CEP-06	HTML Email with Inline Images	Medium	suite/smtpclient_email-composition/test.cep-06.html-inline-images.ts
CEP-07	Custom Headers	Low	suite/smtpclient_email-composition/test.cep-07.custom-headers.ts
CEP-08	Message-ID Generation	Medium	suite/smtpclient_email-composition/test.cep-08.message-id.ts
CEP-09	Date Header Formatting	Medium	suite/smtpclient_email-composition/test.cep-09.date-formatting.ts
CEP-10	Line Length Limits (RFC 5322)	High	suite/smtpclient_email-composition/test.cep-10.line-length-limits.ts

13. Client Security (CSEC)

Tests for client-side security features and protections.

ID	Test Description	Priority	Implementation
CSEC-01	TLS Certificate Verification	High	suite/smtpclient_security/test.csec-01.tls-verification.ts
CSEC-02	Authentication Mechanisms	High	suite/smtpclient_security/test.csec-02.auth-mechanisms.ts
CSEC-03	OAuth2 Support	Medium	suite/smtpclient_security/test.csec-03.oauth2-support.ts
CSEC-04	Password Security (No Plaintext)	High	suite/smtpclient_security/test.csec-04.password-security.ts
CSEC-05	DKIM Signing	High	suite/smtpclient_security/test.csec-05.dkim-signing.ts
CSEC-06	SPF Record Compliance	Medium	suite/smtpclient_security/test.csec-06.spf-compliance.ts
CSEC-07	Secure Credential Storage	High	suite/smtpclient_security/test.csec-07.credential-storage.ts
CSEC-08	TLS Version Enforcement	High	suite/smtpclient_security/test.csec-08.tls-version-enforcement.ts
CSEC-09	Certificate Pinning	Low	suite/smtpclient_security/test.csec-09.certificate-pinning.ts
CSEC-10	Injection Attack Prevention	High	suite/smtpclient_security/test.csec-10.injection-prevention.ts

14. Client Error Handling (CERR)

Tests for how the client handles various error conditions.

ID	Test Description	Priority	Implementation
CERR-01	4xx Error Response Handling	High	suite/smtpclient_error-handling/test.cerr-01.4xx-errors.ts
CERR-02	5xx Error Response Handling	High	suite/smtpclient_error-handling/test.cerr-02.5xx-errors.ts
CERR-03	Network Failure Recovery	High	suite/smtpclient_error-handling/test.cerr-03.network-failures.ts
CERR-04	Timeout Recovery	High	suite/smtpclient_error-handling/test.cerr-04.timeout-recovery.ts
CERR-05	Retry Logic with Backoff	High	suite/smtpclient_error-handling/test.cerr-05.retry-backoff.ts
CERR-06	Greylisting Handling	Medium	suite/smtpclient_error-handling/test.cerr-06.greylisting.ts
CERR-07	Rate Limit Response Handling	High	suite/smtpclient_error-handling/test.cerr-07.rate-limits.ts
CERR-08	Malformed Server Response	Medium	suite/smtpclient_error-handling/test.cerr-08.malformed-responses.ts
CERR-09	Connection Drop During Transfer	High	suite/smtpclient_error-handling/test.cerr-09.connection-drops.ts
CERR-10	Authentication Failure Handling	High	suite/smtpclient_error-handling/test.cerr-10.auth-failures.ts

15. Client Performance (CPERF)

Tests for client performance characteristics and optimization.

ID	Test Description	Priority	Implementation
CPERF-01	Bulk Email Sending	High	suite/smtpclient_performance/test.cperf-01.bulk-sending.ts
CPERF-02	Connection Pool Efficiency	High	suite/smtpclient_performance/test.cperf-02.pool-efficiency.ts
CPERF-03	Memory Usage Under Load	High	suite/smtpclient_performance/test.cperf-03.memory-usage.ts
CPERF-04	CPU Usage Optimization	Medium	suite/smtpclient_performance/test.cperf-04.cpu-optimization.ts
CPERF-05	Parallel Sending Performance	High	suite/smtpclient_performance/test.cperf-05.parallel-sending.ts
CPERF-06	Large Attachment Handling	Medium	suite/smtpclient_performance/test.cperf-06.large-attachments.ts
CPERF-07	Queue Management	High	suite/smtpclient_performance/test.cperf-07.queue-management.ts
CPERF-08	DNS Caching Efficiency	Medium	suite/smtpclient_performance/test.cperf-08.dns-caching.ts

16. Client Reliability (CREL)

Tests for client reliability and resilience.

ID	Test Description	Priority	Implementation
CREL-01	Long Running Stability	High	suite/smtpclient_reliability/test.crel-01.long-running.ts
CREL-02	Failover to Backup MX	High	suite/smtpclient_reliability/test.crel-02.mx-failover.ts
CREL-03	Queue Persistence	High	suite/smtpclient_reliability/test.crel-03.queue-persistence.ts
CREL-04	Crash Recovery	High	suite/smtpclient_reliability/test.crel-04.crash-recovery.ts
CREL-05	Memory Leak Prevention	High	suite/smtpclient_reliability/test.crel-05.memory-leaks.ts
CREL-06	Concurrent Operation Safety	High	suite/smtpclient_reliability/test.crel-06.concurrency-safety.ts
CREL-07	Resource Cleanup	Medium	suite/smtpclient_reliability/test.crel-07.resource-cleanup.ts

17. Client Edge Cases (CEDGE)

Tests for unusual scenarios and edge cases.

ID	Test Description	Priority	Implementation
CEDGE-01	Extremely Slow Server Response	Medium	suite/smtpclient_edge-cases/test.cedge-01.slow-server.ts
CEDGE-02	Server Sending Invalid UTF-8	Low	suite/smtpclient_edge-cases/test.cedge-02.invalid-utf8.ts
CEDGE-03	Extremely Large Recipients List	Medium	suite/smtpclient_edge-cases/test.cedge-03.large-recipient-list.ts
CEDGE-04	Zero-Byte Attachments	Low	suite/smtpclient_edge-cases/test.cedge-04.zero-byte-attachments.ts
CEDGE-05	Server Disconnect Mid-Command	High	suite/smtpclient_edge-cases/test.cedge-05.mid-command-disconnect.ts
CEDGE-06	Unusual Server Banners	Low	suite/smtpclient_edge-cases/test.cedge-06.unusual-banners.ts
CEDGE-07	Non-Standard Port Connections	Medium	suite/smtpclient_edge-cases/test.cedge-07.non-standard-ports.ts

18. Client RFC Compliance (CRFC)

Tests for RFC compliance from the client perspective.

ID	Test Description	Priority	Implementation
CRFC-01	RFC 5321 Client Requirements	High	suite/smtpclient_rfc-compliance/test.crfc-01.rfc5321-client.ts
CRFC-02	RFC 5322 Message Format	High	suite/smtpclient_rfc-compliance/test.crfc-02.rfc5322-format.ts
CRFC-03	RFC 2045-2049 MIME Compliance	High	suite/smtpclient_rfc-compliance/test.crfc-03.mime-compliance.ts
CRFC-04	RFC 4954 AUTH Extension	High	suite/smtpclient_rfc-compliance/test.crfc-04.auth-extension.ts
CRFC-05	RFC 3207 STARTTLS	High	suite/smtpclient_rfc-compliance/test.crfc-05.starttls.ts
CRFC-06	RFC 1870 SIZE Extension	Medium	suite/smtpclient_rfc-compliance/test.crfc-06.size-extension.ts
CRFC-07	RFC 6152 8BITMIME Extension	Medium	suite/smtpclient_rfc-compliance/test.crfc-07.8bitmime.ts
CRFC-08	RFC 2920 Command Pipelining	Medium	suite/smtpclient_rfc-compliance/test.crfc-08.pipelining.ts

Running SMTP Client Tests

Run All Client Tests

cd dcrouter
pnpm test test/suite/smtpclient_*

Run Specific Client Test Category

# Run all client connection tests
pnpm test test/suite/smtpclient_connection

# Run all client security tests
pnpm test test/suite/smtpclient_security

Run Single Client Test File

# Run basic TCP connection test
tsx test/suite/smtpclient_connection/test.ccm-01.basic-tcp-connection.ts

# Run AUTH mechanisms test
tsx test/suite/smtpclient_commands/test.ccmd-05.auth-mechanisms.ts

Client Performance Benchmarks

Expected performance metrics for production-ready SMTP client:

• Sending Rate: >100 emails per second (with connection pooling)
• Connection Pool Size: 10-50 concurrent connections efficiently managed
• Memory Usage: <500MB for 1000 concurrent email operations
• DNS Cache Hit Rate: >90% for repeated domains
• Retry Success Rate: >95% for temporary failures
• Large Attachment Support: Files up to 25MB without performance degradation
• Queue Processing: >1000 emails/minute with persistent queue

Client Security Requirements

All client security tests must pass for production deployment:

• TLS Support: TLS 1.2+ required, TLS 1.3 preferred
• Authentication: Support for LOGIN, PLAIN, CRAM-MD5, OAuth2
• Certificate Validation: Proper certificate chain validation
• DKIM Signing: Automatic DKIM signature generation
• Credential Security: No plaintext password storage
• Injection Prevention: Protection against header/command injection

Client Production Readiness Criteria

Production Gate 1: Core Functionality (>95% tests passing)

• Basic connection establishment
• Command execution and response parsing
• Email composition and sending
• Error handling and recovery

Production Gate 2: Advanced Features (>90% tests passing)

• Connection pooling and reuse
• Authentication mechanisms
• TLS/STARTTLS support
• Retry logic and resilience

Production Gate 3: Enterprise Ready (>85% tests passing)

• High-volume sending capabilities
• Advanced security features
• Full RFC compliance
• Performance under load

Key Differences: Server vs Client Tests

Aspect	Server Tests	Client Tests
Focus	Accepting connections, processing commands	Making connections, sending commands
Security	Validating incoming data, enforcing policies	Protecting credentials, validating servers
Performance	Handling many clients concurrently	Efficient bulk sending, connection reuse
Reliability	Staying up under attack/load	Retrying failures, handling timeouts
RFC Compliance	Server MUST requirements	Client MUST requirements

Test Implementation Priority

1. Critical (implement first):

   • Basic connection and command sending
   • Authentication mechanisms
   • Error handling and retry logic
   • TLS/Security features

2. High Priority (implement second):

   • Connection pooling
   • Email composition and MIME
   • Performance optimization
   • RFC compliance

3. Medium Priority (implement third):

   • Advanced features (OAuth2, etc.)
   • Edge case handling
   • Extended performance tests
   • Additional RFC extensions

4. Low Priority (implement last):

   • Proxy support
   • Certificate pinning
   • Unusual scenarios
   • Optional RFC features