Email Providers

Process CloudMailin normalized message POSTs

Select normalized JSON or multipart deliberately and durably process envelope, headers, body, and attachments without using deprecated payload assumptions.

Reviewed October 25, 2026

CloudMailin offers normalized JSON, normalized multipart, and raw-message post formats. Its format reference distinguishes these from older formats retained for legacy applications.

Match the parser to the configured format

Select normalized JSON or multipart for a new parsed-message integration, following the provider’s recommendation for your framework.
Implement endpoint authentication before accepting the message as work.
Parse the documented envelope, headers, body, and attachments structure for that format.
Use envelope recipient information for delivery routing rather than assuming the sender-controlled To header identifies every actual recipient.

If selecting raw-message format, use a maintained MIME parser. A raw message is not already JSON, and multipart file parts cannot be processed by a JSON-only handler.

Persist before acknowledgement

Store authenticated work durably, deduplicate according to stable message/delivery identity, and make downstream actions independently idempotent. Apply body/attachment limits and retention before accepting public traffic.

Test a plain message, allowed attachment, duplicate, malformed request, and temporary receiver failure using non-sensitive content. Use CloudMailin’s documented HTTP-response/retry semantics rather than assuming unlimited retries.

Do not point a CloudMailin request at MailKite’s verifier and expect it to validate. A migration requires routing, callback security, and payload mapping changes together, even when both services deliver structured email.