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Upyo changelog ​

Version 0.4.0 ​

Released on December 25, 2025. Happy Holidays!

@upyo/core ​

  • Added idempotencyKey property to Message interface. [#16]

    This allows users to provide their own idempotency key for request deduplication when retrying failed send operations. By including the key in the message itself, retries become simpler—just resend the same message object. If not provided, transports may generate their own key internally (behavior varies by transport implementation).

@upyo/smtp ​

  • Added DKIM (DomainKeys Identified Mail) signing support. [#18]

    Outgoing emails can now be signed with DKIM for improved deliverability and authentication. The implementation uses the standard Web Crypto API for cross-runtime compatibility (Node.js, Deno, Bun, edge functions).

    • Added DkimConfig interface for configuring DKIM signing.
    • Added DkimSignature interface for individual signature settings.
    • Added DkimAlgorithm type supporting rsa-sha256 (RFC 6376) and ed25519-sha256 (RFC 8463).
    • Added DkimCanonicalization type for header/body canonicalization.
    • Added DkimSigningFailureAction type (throw or send-unsigned).
    • Supports multiple DKIM signatures per message.
    • Configurable failure handling: throw error or send unsigned.
    • Accepts both PEM strings and CryptoKey objects for private keys.

@upyo/jmap ​

  • Added JMAP transport for sending emails via JMAP protocol. [#10]

    JMAP (JSON Meta Application Protocol) is a modern, efficient protocol for email access and submission, defined in RFC 8620 (core) and RFC 8621 (mail). This transport provides:

    • Automatic session discovery and caching
    • Automatic identity resolution from sender email
    • Bearer token authentication
    • Exponential backoff retry with configurable attempts
    • Request timeout and AbortSignal support
    • Text and HTML message content (multipart/alternative)
    • Priority headers (X-Priority, Importance)
    • Custom headers
    • File attachments via blob upload
    • Inline attachments (multipart/related)

@upyo/resend ​

  • Added support for user-provided idempotency keys via Message.idempotencyKey. [#16]

    Each message can now include an idempotencyKey to ensure it is not sent multiple times during retries. For batch operations via sendMany(), the first message's key is used for the entire batch request. If not provided, a unique key is automatically generated for each request.

Version 0.3.4 ​

Released on December 18, 2025.

@upyo/resend ​

  • Fixed idempotency key not being sent as an HTTP request header. [#16]

    The Resend transport was incorrectly adding the Idempotency-Key to the email's custom headers inside the JSON payload, but the Resend API expects it as an HTTP request header. This fix moves the idempotency key to the proper location.

Version 0.3.3 ​

Released on December 13, 2025.

@upyo/core ​

  • Fixed a potential SMTP command injection vulnerability.

    Email addresses are now validated to prevent newline characters (\r or \n), which could be used to inject malicious SMTP commands.

Version 0.3.2 ​

Released on December 12, 2025.

@upyo/ses ​

  • Fixed headers serialization issue on edge runtimes. [#15]

    The SES transport now converts the Headers object to a plain object before passing to fetch(), which resolves “Missing Authentication Token” errors on edge runtimes like Bunny CDN Edge that don't properly serialize Headers objects.

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]

@upyo/plunk ​

@upyo/resend ​

Version 0.2.4 ​

Released on December 13, 2025.

@upyo/core ​

  • Fixed a potential SMTP command injection vulnerability.

    Email addresses are now validated to prevent newline characters (\r or \n), which could be used to inject malicious SMTP commands.

Version 0.2.3 ​

Released on December 12, 2025.

@upyo/ses ​

  • Fixed headers serialization issue on edge runtimes. [#15]

    The SES transport now converts the Headers object to a plain object before passing to fetch(), which resolves “Missing Authentication Token” errors on edge runtimes like Bunny CDN Edge that don't properly serialize Headers objects.

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 ​

@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.