ViaVox

Sync Microsoft 365 calendar (and soon contacts) into Nextcloud.

ViaVox is the Nextcloud companion app for the ViaVox Syncer service: a webhook-based Microsoft Graph → Nextcloud CalDAV bridge that keeps Outlook / Exchange Online calendars in sync with each Nextcloud user's personal calendar, both directions, in near-real-time.

This repo distributes the Nextcloud app half of the stack. The companion syncer service is deployed separately (admins configure its URL + shared token).

What it does

• Each Nextcloud user can connect / disconnect their own Microsoft 365 account from Settings → Personal → ViaVox.
• Once connected, Outlook events flow into the user's personal calendar via webhook notifications (no polling), and edits made in Nextcloud Calendar flow back to Outlook.
• Recurring meetings — including exceptions, cancellations, DST transitions, attendees and RSVPs — are handled end-to-end.
• Duplicate cleanup: surfaces meetings that Exchange minted twice (a fresh vCal-Uid per iTip round-trip, e.g. when a room is added to an existing meeting) and lets the user remove a copy. The delete is fail-closed and provenance-gated — only offered when every copy is provably a Microsoft 365 item — with a per-user lock against concurrent deletes.
• An admin overview shows per-user connection status and sync health, plus an hourly watcher that notifies a user (bell + optional email) if their sync goes offline.

Nextcloud scheduling / iTip is deliberately turned off

Microsoft 365 is the authoritative scheduler for connected users. If Nextcloud also ran its own iTip scheduling, every cross-user meeting would get a second, NC-minted copy and duplicate invitation emails would go out. ViaVox therefore suppresses Nextcloud's built-in calendar scheduling on three layers:

1. No iTip emails — a repair step sets dav.sendInvitations=no on install and after every migration, so Nextcloud never emails iTip invitations/cancellations for connected users.
2. No iTip on the CalDAV path — a Sabre plugin sets x-nc-scheduling: false on every calendar-object PUT/DELETE, short-circuiting Nextcloud's scheduler. This also prevents the 403 ("event cannot be deleted") that NC's scheduler raises when a room/resource attendee is involved.
3. No iTip on internal paths — a listener covers the internal ICreateFromString paths (Talk-scheduled meetings, Calendar bookings / proposals) that bypass the standard CalDAV route.

Microsoft 365 owns invitations and cancellations end to end; Nextcloud mirrors the result without generating its own scheduling traffic.

Install

1. Download the latest viavox-X.Y.Z.tgz release asset (see the Releases page).

2. Extract into your Nextcloud installation's apps/ directory so that apps/viavox/appinfo/info.xml exists:

   tar xzf viavox-0.8.22.tar.gz -C /var/www/nextcloud/apps/
   chown -R www-data:www-data /var/www/nextcloud/apps/viavox
   

3. Enable the app:

   occ app:enable viavox
   

4. As an admin, open Settings → Administration → ViaVox, enter the ViaVox Syncer base URL and shared NC-app token, hit Save and then Test connection.

5. Each user can now open Settings → Personal → ViaVox and click Connect Microsoft 365 to start syncing.

Requirements

• Nextcloud 32 – 34 (verified compatible with Nextcloud 34).
• PHP 8.1 – 8.4.
• A reachable ViaVox Syncer instance (separately deployed).
• A Microsoft 365 tenant with an App Registration that has Calendars.ReadWrite delegated permission.

Operator note: keep dav calendarRetentionObligation unset (the default) while the duplicate-cleanup feature is in use, so a removed copy stays restorable from the Nextcloud trash bin.

License

AGPL-3.0-or-later. See COPYING inside the package.

Support

For installation help or to report issues, contact the maintainer (see appinfo/info.xml for the e-mail address).