Best integration platform for mail and calendar integrations (2026)

This post compares the leading platforms for building mail and calendar API integrations in 2026, evaluating Nango, Nylas, Aurinko, and Unipile across provider coverage, authentication ownership, API accessibility, and AI coding agent support. Nango is highlighted as supporting 800-plus APIs with full API access and user-controlled authentication, while Nylas offers a unified communications API, Aurinko provides a pass-through alternative, and Unipile focuses on messaging. Teams building integrations with Google, Microsoft, and IMAP need to navigate OAuth, incremental sync, and push notifications, making platform choice a critical infrastructure decision.