Sync Posteo Calendar with Google Calendar or Microsoft 365

Posteo is one of the most privacy-friendly email and calendar providers available — hosted in Germany, ad-free, and built around open standards like CalDAV. But there's a problem: Google Calendar and Microsoft 365 don't speak CalDAV. If your workplace uses Google or Microsoft, keeping your Posteo calendar in sync requires a workaround.

The old workaround: Outlook CalDAV Synchronizer

Posteo's own documentation recommends the Outlook CalDAV Synchronizer — a free, open-source add-in for Outlook. It works well in Classic Outlook, but there's a catch: the new Outlook no longer supports COM Add-ins. As Microsoft rolls out New Outlook via Windows Update, this solution is becoming unreliable for more users every day.

The ICS feed workaround

Posteo lets you generate a public ICS link for your calendar that Google Calendar can subscribe to. It's easy to set up — but it's read-only, and updates only every 24–48 hours. If you book a meeting in Posteo, Google Calendar won't know about it for up to two days. For Calendly users or anyone with a busy schedule, that's not acceptable.

A modern solution: CalDAVconnect

CalDAVconnect is a cloud-based bridge between your Posteo calendar and Google Calendar or Microsoft 365. It connects to your Posteo calendar via CalDAV and syncs changes bidirectionally — in seconds, not hours.

Your Posteo CalDAV URL:

https://posteo.de:8443/calendars/your-username/default

(Replace your-username with the part of your Posteo address before the @.)

How it works:

Changes in Google Calendar or Microsoft 365 sync to Posteo within 1–2 seconds via webhooks
Changes in Posteo sync to Google or Microsoft within 7–8 seconds on average via lightweight CTag polling
No Outlook add-in required — sync happens in the cloud, independent of any email client

Setup takes less than 5 minutes:

Sign up for CalDAVconnect
Enter your Posteo CalDAV URL and credentials
Connect your Google or Microsoft account via OAuth
Select which calendars to sync

Why this fits Posteo users

Posteo users tend to care about privacy and data sovereignty. CalDAVconnect is hosted in Germany on Hetzner infrastructure in Nuremberg — all data stays within the EU and is encrypted at rest. No data is shared with third parties.

The sync metadata is stored by CalDAVconnect to enable bidirectional sync, but your calendar data never leaves European infrastructure.

CalDAVconnect is currently in public beta and free to use. Join the beta and connect your Posteo calendar in minutes.