Sync Protections

Calendox enforces a small set of always-on safeguards so that syncing can never duplicate your events or loop between calendars: each calendar can be imported only once, can belong to only one sync, and every synced copy is recognizable as a copy. These protections run on every plan with no configuration — this page explains the ones you might encounter.

Why can a calendar be imported only once?

A calendar can be imported into Calendox exactly once — across all Calendox accounts, not just yours. If a calendar is already imported under another account, importing it again is blocked with "Some selected calendars are already imported by another Calendox account."

Two accounts independently syncing the same calendar would create duplicate copies of its events and, at worst, feed each other's syncs in a loop. If you genuinely need the calendar under a different account, remove it from the account that currently has it first, then import it where you want it.

Why can a calendar belong to only one sync?

Each calendar can be a member of only one sync at a time — and syncs in any status count, including Disabled and Failed. Trying to add a calendar that's already in a sync is rejected with "One or more selected calendars are already part of a sync."

The same calendar in two syncs would receive each event twice and could act as a bridge that loops copies between the two syncs. To move a calendar to a new sync, delete its current sync first — deleting a sync also cleans up the copies it created. The related rules for combining calendars are covered in Create your first sync.

Why are some calendars marked Read-only or Not supported?

The import dialog checks the real write access of every calendar on your account:

• Read-only — your provider account can view this calendar but not create events in it, so it can't host synced copies.
• Not supported — the calendar appears in your account but actually belongs to another mailbox (family and group calendars projected by the provider, for example), where writing and change notifications aren't dependable.

Neither can be imported. This keeps every sync writable end-to-end, so a sync you create never silently fails on a calendar that couldn't accept events in the first place.

How does Calendox prevent sync loops?

Two independent, always-on layers:

1. Internal sync metadata. Every event Calendox creates carries internal sync metadata identifying it as a synced copy. When a change notification arrives for an event carrying that metadata, Calendox recognizes its own copy and never copies it again — a copy can never become a new source.
2. An independent second guard. Calendox also detects events that were already mirrored into one of your calendars by another sync tool, and skips them rather than copying them again — so Calendox running alongside another sync product doesn't multiply the events they share.

Together with the import-once and one-sync-per-calendar rules above, this is what makes multi-way sync safe to run in every direction at once.

What happens to my syncs if my subscription lapses?

Syncs are paused, never destroyed:

• Trial ends or subscription expires — your subscription ends and your syncs switch to Disabled with an explanatory banner. Every event already synced stays exactly where it is in your calendars.
• A renewal payment fails — you get a 3-day grace period during which syncs keep running. Only if payment isn't recovered within those 3 days are syncs paused.
• You subscribe again or payment succeeds — syncs are restored automatically and catch up from where they left off, passing through Pending while they do. There's nothing to rebuild and nothing to reconfigure.

See Sync status for every pause reason, including Business and Enterprise license scenarios, and Plans and billing for the billing side.

Next steps

• What is calendar sync? — the overview of both sync types
• Sync status — statuses, pause reasons, and recovery steps
• How Calendox Protects Your Data — the privacy side: no event content stored
• Calendar Sync feature page