alertmanager-graph-bridge

alertmanager-graph-bridge is a lightweight HTTP server that bridges Prometheus Alertmanager webhook notifications to the Microsoft Graph API. It receives Alertmanager webhook payloads, renders them into readable HTML e-mails and sends them through sendMail, authenticating with the OAuth2 client-credentials flow.

Why

Alertmanager has no built-in support for sending mail through Microsoft 365 / Exchange Online via the Graph API. Many organisations have disabled SMTP AUTH and require applications to use Graph with OAuth2 instead. This bridge fills that gap with a single, small Go binary.

Features

• Implements the Alertmanager webhook API (POST /api/v1/alerts).
• Optional bearer-token authentication for incoming requests.
• Health (/healthz), readiness (/readyz) and Prometheus metrics (/metrics) endpoints.
• Microsoft Graph sendMail integration with OAuth2 client credentials and automatic token caching / refresh.
• HTML e-mail rendering that groups multiple alerts into one message, with a selectable modern or classic template.
• Per-alert recipient overrides via the email_to label.
• Configuration through a YAML file and/or AGB_-prefixed environment variables.
• Structured logging (slog) in JSON or text format.

Next steps

• Getting Started - install and run the bridge.
• Configuration - all configuration options.
• Architecture - how the pieces fit together.
• API Reference - the HTTP endpoints and metrics.
• Development - build and test locally.
• End-to-End Testing - testing against the live Microsoft Graph API.
• Quality Criteria - the bar every change is held to.