Upyo changelog

Version 0.4.0

To be released.

Version 0.3.1

Released on November 3, 2025.

@upyo/smtp

• Added STARTTLS support for secure connection upgrade. The SMTP transport now automatically detects and uses STARTTLS when connecting to servers that advertise this capability (such as Protonmail, Office 365, and others). This allows using port 587 with secure: false for automatic encryption upgrade. [#14]

Version 0.3.0

Released on September 16, 2025.

@upyo/pool

• Added pool transport for combining multiple email providers with load balancing and failover strategies. [#8]

  • Added PoolTransport class with AsyncDisposable support.
  • Added PoolConfig interface.
  • Added ResolvedPoolConfig type.
  • Added TransportEntry interface.
  • Added ResolvedTransportEntry type.
  • Added PoolStrategy type for built-in strategies.
  • Added Strategy interface for custom routing logic.
  • Added TransportSelection interface.
  • Added RoundRobinStrategy class for equal distribution.
  • Added WeightedStrategy class for proportional distribution.
  • Added PriorityStrategy class for failover-based routing.
  • Added SelectorBasedStrategy class for content-based routing.
  • Support for round-robin, weighted, priority, and selector-based strategies.
  • Automatic failover and retry logic with configurable limits.
  • Comprehensive error aggregation across multiple providers.

@upyo/plunk

• Added Plunk transport. [#11]

  • Added PlunkTransport class.
  • Added PlunkConfig interface.
  • Added ResolvedPlunkConfig interface.
  • Added PlunkError interface.
  • Added PlunkResponse interface.
  • Support for both cloud-hosted and self-hosted Plunk instances.

@upyo/resend

• Added Resend transport. [#9]

  • Added ResendTransport class.
  • Added ResendConfig interface.
  • Added ResolvedResendConfig interface.
  • Added ResendApiError interface.
  • Added ResendBatchResponse interface.
  • Added ResendError interface.
  • Added ResendResponse interface.

Version 0.2.2

Released on November 3, 2025.

@upyo/smtp

• Added STARTTLS support for secure connection upgrade. The SMTP transport now automatically detects and uses STARTTLS when connecting to servers that advertise this capability (such as Protonmail, Office 365, and others). This allows using port 587 with secure: false for automatic encryption upgrade. [#14]

Version 0.2.1

Released on August 4, 2025.

@upyo/smtp

• Fixed “Maximum call stack size exceeded” error when sending large attachments. [#6]

  The SMTP transport now uses Buffer.from().toString('base64') instead of the legacy btoa() function for base64 encoding, which resolves stack overflow issues with large attachments (e.g., 500KB+ files).

• Fixed UTF-8 encoding issue where email addresses were incorrectly encoded in SMTP headers. [#7]

  Only display names are now encoded using RFC 2047 encoding, while email addresses remain unencoded. For example, German ÄÖÜ <info@example.com> now correctly becomes =?UTF-8?B?...?= <info@example.com> instead of encoding the entire string including the email address.

Version 0.2.0

Released on July 17, 2025.

@upyo/core

• Improved type safety by making array fields readonly.

  • Changed the type of Message.recipients property from Address[] to readonly Address[].
  • Changed the type of Message.ccRecipients property from Address[] to readonly Address[].
  • Changed the type of Message.bccRecipients property from Address[] to readonly Address[].
  • Changed the type of Message.replyRecipients property from Address[] to readonly Address[].
  • Changed the type of Message.attachments property from Attachment[] to readonly Attachment[].
  • Changed the type of Message.tags property from string[] to readonly string[].

• Enhanced email address type safety with template literal types.

  • Added EmailAddress type.
  • Changed Address.address property type from string to EmailAddress.
  • Added isEmailAddress() type guard function for runtime email validation.

@upyo/ses

• Added Amazon SES transport. [#3]

  • Added SesTransport class.
  • Added SesConfig interface.
  • Added SesAuthentication interface.

@upyo/opentelemetry

• Added OpenTelemetry observability support. [#5]

  • Added OpenTelemetryTransport class.
  • Added OpenTelemetryConfig interface.
  • Added ObservabilityConfig interface.
  • Added MetricsConfig interface.
  • Added TracingConfig interface.
  • Added AttributeExtractor type.
  • Added ErrorClassifier type.
  • Added createErrorClassifier() function.
  • Added defaultErrorClassifier() function.
  • Added AutoConfig interface.
  • Added createOpenTelemetryTransport() function.
  • Added CreateOpenTelemetryTransportConfig interface.
  • Added createEmailAttributeExtractor() function.

Version 0.1.2

Released on Nowember 3, 2025.

@upyo/smtp

• Added STARTTLS support for secure connection upgrade. The SMTP transport now automatically detects and uses STARTTLS when connecting to servers that advertise this capability (such as Protonmail, Office 365, and others). This allows using port 587 with secure: false for automatic encryption upgrade. [#14]

Version 0.1.1

Released on July 14, 2025.

@upyo/smtp

• Fixed CJK character encoding corruption in SMTP transport HTML emails. Korean, Japanese, and Chinese characters are now properly encoded using UTF-8 quoted-printable encoding. [#4]

Version 0.1.0

Initial release. Released on July 13, 2025.