Welcome to the mailbox user forum

New Topic

Caldav server error and not RFC compliant

Christopher Online shared this idea ago

Proposed

Trying to sync a repeating task to the mailbox.org caldav server from a iOS client app and run into the error which you can see at the very end of this message. Furthermore I received the feedback that the mailbox.org caldav server is apparently it RFC compliant:

“ I can see the CalDAV server in particular is picky about BusyCal sending DTSTART == DUE (this isn't strictly RFC compliant but many servers out there would fail to work if they weren't equal). We'll have to add a workaround for the next upcoming update for this to work.”

Error log:

026-04-26 12:37:25 B -1- CalDAVSyncTask (31187546-3C9E-4F57-9EAF-42D3795C9422): push UPDATE event Asdf daily (DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D) to calendar Repeating (etag: ignore)

2026-04-26 12:37:25 M -2- send request =>

PUT https://dav.mailbox.org/caldav/NTE/DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D.ics

User-Agent: BusyCal-6.6.0 (Calendar) Mac OS X/13.0.1

Content-Type: text/calendar

Authorization: <>

Cache-Control: no-cache

BEGIN:VCALENDAR

VERSION:2.0

PRODID:-//BusyApps//BusyCaliOS 6.6.0//EN

CALSCALE:GREGORIAN

BEGIN:VTODO

DTSTART;VALUE=DATE:20260426

DUE;VALUE=DATE:20260426

RRULE:FREQ=WEEKLY;INTERVAL=2

SUMMARY:Asdf daily

UID:DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D

SEQUENCE:1

DTSTAMP:20260426T103725Z

CREATED:20260422T121912Z

LAST-MODIFIED:20260426T103722Z

X-BUSYMAC-LASTMODBY:iPhone

END:VTODO

END:VCALENDAR

2026-04-26 12:37:25 B -1- received 400 response =>

HTTP 400

URL: https://dav.mailbox.org/caldav/NTE/DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D.ics

Content-Type: text/xml; charset=UTF-8

x-powered-by: Open-Xchange

x-xss-protection: 1; mode=block

x-download-options: noopen

Content-Encoding: gzip

x-permitted-cross-domain-policies: none

referrer-policy: no-referrer

Date: Sun, 26 Apr 2026 10:37:25 GMT

x-robots-tag: noindex, nofollow

Strict-Transport-Security: max-age=15552000; includeSubDomains; preload;

feature-policy: accelerometer 'none'; camera 'none'; gyroscope 'none'; magnetometer 'none'; microphone 'none'; usb 'none';

x-content-type-options: nosniff

Vary: Accept-Encoding

<?xml version="1.0" encoding="UTF-8"?>

<D:error xmlns:D="DAV:" xmlns:OX="http://ox.io/ns/">

<OX:error>An error occurred inside the server which prevented it from fulfilling the request.</OX:error>

<OX:category>ERROR</OX:category>

<OX:code>WEBDAV-1000</OX:code>

<OX:error_id>2030185343-1865961</OX:error_id>

<OX:error_desc>A WebDAV error occurred. (HTTP 400)</OX:error_desc>

</D:error>

2026-04-26 12:37:25 B -0- CalDAVSyncTask (31187546-3C9E-4F57-9EAF-42D3795C9422): server returned 400, retrying with compatibility export for event Asdf daily (DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D) [omit equal task due]

2026-04-26 12:37:25 B -2- CalDAVSyncTask (31187546-3C9E-4F57-9EAF-42D3795C9422): will try and update again to: (null)

2026-04-26 12:37:25 B -2- CalDAVSyncTask (31187546-3C9E-4F57-9EAF-42D3795C9422): updated SEQUENCE for event Asdf daily (DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D) to: 1

2026-04-26 12:37:25 B -1- CalDAVSyncTask (31187546-3C9E-4F57-9EAF-42D3795C9422): retrying push without equal task DUE for event Asdf daily (DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D)

2026-04-26 12:37:25 B -1- CalDAVSyncTask (31187546-3C9E-4F57-9EAF-42D3795C9422): push UPDATE event Asdf daily (DAE7DFA7-8561-4B6B-A239-4FDB6E293A8D) to calendar Repeating (etag: ignore)