Fetchmail Adapter for Exchange Online / Graph API

Challenge

After migrating to Exchange Online, an existing business application still required a Fetchmail-compatible interface and could not be modified.

Approach

I built a Go-based drop-in replacement for Fetchmail with OAuth2 and Graph API integration. The tool reproduces expected Fetchmail behavior, adds robust retry and logging, and implements secure token/TLS handling.

Snapshot

  • Industry: Industrial enterprise
  • Time frame: 2024
  • Technologies
    • Go (custom implementation)
    • Microsoft Graph API
    • OAuth2 / TLS
    • Exchange Online

The solution kept the commercial legacy software running unchanged and established a stable bridge to modern cloud mail infrastructure.

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With lean, custom tools I close integration gaps in critical production environments - reliable, robust, and maintainable.

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