La Poste Colissimo Web Service (SOAP, France)

Colissimo Web Service is La Poste's SOAP and WSDL surface for Colissimo parcel shipments originating in France. It exposes label generation, return-label generation, document retrieval, and supporting lookups through a single WSDL. Authentication is account-number plus password embedded in the SOAP request body — the credentials ride inside every envelope, so credential hygiene is a per-call concern, not a session concern. Documentation is primarily in French and many operational fields (such as the Colissimo product code, signature options, and customs declarations for non-EU destinations) are validated server-side against rules that are easier to read in the official French-language guide than in any English secondary source. Schema validation against the WSDL and imported XSDs before sending the request turns vague server-side faults into precise local errors. Operationally, label artifacts are returned as base64-encoded payloads in the SOAP response body, and the most common first-incident is mishandling the binary payload during XML parsing — particularly when the response includes both PDF labels and CN23 customs documents. Treat WSDL drift as a real risk: La Poste publishes updated WSDLs when product rules change, and integrators that miss the diff will hit silent contract regressions on the next batch run. Pair the integration with WSDL diff monitoring and a generated-client refresh workflow.