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Outlook CalDAV Synchronizer Alternative for New Outlook Users

· 3 min read
Outlook CalDAV Microsoft 365 SOGo Nextcloud

If you've been using the Outlook CalDAV Synchronizer to sync your Nextcloud or SOGo calendar with Outlook, you may have noticed that it stopped working after upgrading to the new Outlook. You're not alone — and there's a reason for it.

What happened to the Outlook CalDAV Synchronizer?

The Outlook CalDAV Synchronizer is a popular open-source tool that has been helping users sync CalDAV calendars with Outlook Desktop for years. It works as a COM Add-in — a type of plugin that integrates directly into Outlook's desktop application.

In 2024, Microsoft began rolling out the new Outlook for Windows, which is built on a completely different architecture. The new Outlook is essentially a web app (based on Outlook Web Access) and does not support COM Add-ins. This means:

  • The Outlook CalDAV Synchronizer cannot be installed on the new Outlook
  • There is no migration path — COM Add-ins are architecturally incompatible
  • Microsoft has no plans to re-introduce COM Add-in support

For users of SOGo, Nextcloud, Radicale, or Baikal who relied on this tool, this is a significant problem.

Why SOGo users are especially affected

SOGo's official website still recommends the Outlook CalDAV Synchronizer as the way to connect SOGo calendars with Outlook. Unfortunately, this recommendation is now outdated for anyone using the new Outlook.

SOGo does offer ActiveSync support through its SOGo Connector, but this only works with Outlook Desktop — not with the cloud-based Microsoft 365 calendars that the new Outlook uses.

The alternative: Cloud-based sync with CalDAVconnect

Instead of relying on a client-side plugin, CalDAVconnect takes a different approach: it syncs your CalDAV calendar with Microsoft 365 (or Google Calendar) through the cloud.

Here's how it works:

  1. CalDAVconnect connects to your CalDAV server (Nextcloud, SOGo, Radicale, or Baikal) using the standard CalDAV protocol
  2. It connects to your Microsoft 365 account via Microsoft's Graph API
  3. Changes are synced bidirectionally in real-time — when you create an event in SOGo, it appears in Outlook within seconds, and vice versa

Because the sync happens server-to-server, it doesn't matter which Outlook version you use. Whether you're on the new Outlook, Outlook Desktop, Outlook Web, or even the Outlook mobile app — your events are always in sync.

Key differences

| Feature | Outlook CalDAV Synchronizer | CalDAVconnect | |---|---|---| | Sync method | COM Add-in (client-side) | Cloud service (server-to-server) | | New Outlook support | No | Yes | | Outlook Desktop support | Yes | Yes (via Microsoft 365) | | Mobile sync | No | Yes (via Microsoft 365) | | Setup required per device | Yes | No — one-time cloud setup | | Bidirectional | Yes | Yes | | Real-time sync | Only when Outlook is open | Always (webhook-based) |

Getting started

CalDAVconnect is currently in public beta — free to use during the beta period.

  1. Sign up for CalDAVconnect
  2. Add your CalDAV server credentials (SOGo, Nextcloud, Radicale, or Baikal)
  3. Connect your Microsoft 365 account via OAuth
  4. Select which calendars to sync
  5. Your first sync starts automatically

The entire setup takes about 5 minutes. No client-side installation required.

Conclusion

The Outlook CalDAV Synchronizer served the community well for many years, but the shift to the new Outlook has made it obsolete for a growing number of users. CalDAVconnect provides a modern, cloud-based alternative that works with any Outlook version — and syncs in real-time without requiring software on every device.

If you're a SOGo or Nextcloud user who lost your Outlook calendar sync, give CalDAVconnect a try. It's free during the beta.