Zoho

Zoho One is a all-in-one suite to run your entire business. It includes CalDAV calendars and CardDAV contacts.

There are various problems when synchronizing with Zoho (see below).

DAVx⁵ settings

CalDAV Base URL: https://calendar.zoho.com/ or https://calendar.zoho.eu/ (depending on where you have created the account)

CardDAV Base URL: https://contacts.zoho.com/ or https://contacts.zoho.eu/

User name and pasword: your Zoho email address and password. If you're using two-factor authentication, you have to generate and use an application-specific password for DAVx⁵.

CalDAV:

(Mar 2026) There are reports about locally disappearing events during synchronization. During investigation, we couldn't reliably reproduce the problem and also couldn't find a problem on DAVx5 side, but multiple problems on the server side (see below). If you have further information or clear indication that this is a DAVx5 problem, please post there.
(Mar 2026) Invalid behavior: The server returns an empty event list when using Collection Sync (RFC 6578) REPORT with empty sync-token (initial sync). So when you set the “past event time limit” to empty in DAVx5, all events will locally disappear because the server says there are no events. Do not set the “past event time limit” to empty (All entries will be synchronized) until this is fixed by Zoho.
(Mar 2026) Invalid behavior: The server returns varying ETags for the same event, depending on how the event is fetched (REPORT vs GET).
VTODO tasks don't seem to be supported by Zoho.

CardDAV:

vCard contact groups are not supported. Choose the method used by your other clients or "per-contact categories" to minimize potential problems.
Contacts from the "Organization" address book are not provided via CardDAV and can't be synchronized.