CloudMailin vs Stalwart mail-parser

CloudMailin receives email and delivers it to web applications through HTTP POST webhooks. Inbound messages can arrive as JSON, multipart form data, or raw text; attachments can be forwarded to a webhook or stored in Amazon S3, Azure Storage, or Google Cloud Storage. It also sends transactional email through an API or SMTP relay. Outbound tools include spam checks, link and open tracking, bounce handling, reporting, tagging, and priority queues. Inbound delivery history includes 30 days of searchable records with error and retry details, while metadata retention is listed as 60 days. CloudMailin says its inbound service works with any language or framework, naming examples from Node.js and Python to Java and C#. The service was founded in 2010 and is available through an API and the web. A free plan allows 10,000 emails per month and 512KB per message. Paid plans start at $25 a month; the listed options include different email and message-size limits. A seven-day trial is also listed.

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.