CYNC

About CYNC

I built CYNC because the usual way to get company contacts onto everyone's phone was a PowerShell script over EWS, and EWS is being retired. CYNC is a Windows service that runs on your own server and copies your Entra ID users into the contact folder of each Exchange Online mailbox on a schedule, through Microsoft Graph only. What it does: delta sync that fetches only changed users, parallel batched updates across mailboxes, contact matching that survives renames and email changes, certificate-based Entra ID auth, a WinUI 3 admin app for configuration, manual runs and history, remote administration over gRPC for Server Core, MSI installer with silent install, failure notifications to Teams, Slack or Telegram. Pricing: up to 10 users is free with no time limit and no license. Above that it is 0.29 EUR per user per month, dropping with volume to 0.18 EUR with annual billing. 14 day refund if it does not work as described. Runs on Windows Server 2019 or later, or Windows 10 1809 or later. The software is proprietary and runs on your own machine; the only thing that leaves your network is the license check.