MailFrame vs Stalwart mail-parser

MailFrame is a developer-first API that turns raw email into JSON validated against a schema. A request can include raw RFC 822 MIME or plain-text email-like input and a JSON Schema, with validated JSON returned synchronously. Developers can provide an inline schema without registering or choose from prebuilt schemas covering Stripe and Shopify receipts or orders, PayPal, Amazon, Apple App Store and Google Play receipts, GitHub notifications, invoices, travel bookings, and shipping notifications. Signed HMAC-SHA256 webhook delivery supports retries, attempt history, a dead-letter queue, and replay, for downstream systems that accept webhooks. The current API accepts raw MIME and plain-text input; PDF and image parsing are planned, not currently supported. MailFrame says it retains email content only as long as needed for delivery and debugging, does not sell or share customer data, and stores API keys in hashed form. The service is in limited early access, onboarding developers in weekly batches. The Free plan provides 100 parse operations per month without a credit card; paid plans start at $19 per month. SOC 2 Type II is on the roadmap, and MailFrame says it is not yet HIPAA-eligible as a Business Associate.

Stalwart mail-parser is a free, open-source Rust library for parsing email messages. It supports Internet Message Format RFC 5322, MIME RFC 2045–2049 and other internet messaging RFCs, while attempting to handle messages that depart moderately from those standards. Parsed output includes a MIME tree, text and HTML body lists, and attachments. If one alternative is missing, the library can convert HTML to plain text or plain text to HTML. SIMD kernels accelerate scanning on supported targets, while transfer decoding and charset conversion wait until content is read. Returned strings generally reference the original input message. WHATWG encoding labels are recognized, and the optional full_encoding feature adds legacy multibyte sets including Shift_JIS, Big5 and GB18030. Defaults allow nesting depth 64, 10,000 MIME parts and three decoded nested-message levels. Rust 1.98 is required. No feature is enabled by default; serde adds serialization. The library is licensed under MIT or Apache-2.0 and costs nothing.