Best integration platform for mail and calendar integrations (2026) (opens in new tab)

TL;DR If you need email and calendar API integrations in your product, building them involves handling OAuth across Google, Microsoft, and IMAP, incremental sync, and push notifications. This post compares the platforms teams use to build mail and calendar integrations in 2026. We rank them on provider coverage, how you build integrations with each one (including AI coding agent support), how much of the underlying API you can reach, who owns auth, and what else the platform can integrate whe...