[Bug]: Nextcloud calender reminder & invitation notifications are broken

[dzatoah]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

The reminder notifications and invitations behaviour is unpredictable and pretty random. Something is definitely broken.
I could reproduce this issue in Nextcloud 25 RC2 and various older production Nextcloud 24's

Two scenarios:

Send reminder notifications to calendar sharees as well set to off:

What should happen with a private calender:

The organizer creates a calendar entry and invites one person.

• Organizer and invitee get an invitation
• Organizer and invitee get a reminder notification (Error: here in the setup both always get two reminders, so one too many)

What should happen with a group calender:

The organizer creates a calendar entry and invites one person.

• Organizer gets an invitation
• Invitee doesn't get an invitation. (Error: The invitee does not receive an invitation!)
• Organizer and invitee get a reminder (Error: The reminder is not sent e.g. 5 minutes before but only at the time of the appointment)

Send reminder notifications to calendar sharees as well set to on:

Then everyone in the group will receive a notification even though they are not included in the appointment as a participant. That's how it's intended. (So the principle is correct. So only the invitation is missing here.)

So the boil down the issues:

1. Private calender, off -> double notifications
2. Group calendar -> Invitees doesn't get invitation (Invitees should always get an invitation)
3. Group calendar, off -> reminder notifications are sent only at exact appointment time

Probably related:

• Calendar sends duplicate notifications if there is an additional attendee [$250] #21370
• event reminder is missing in a shared calendar w/o edit rights #22441
• Rename setting 'sendEventRemindersToSharedGroupMembers' -> 'sendEventRemindersToSharedUsers'. #31660
• Fix #31303: Make reminder notification behaviour selectable.. #31337

Thanks to @mircokam for spotting this issues.

Steps to reproduce

1. Create a group calendar
2. Add member to group calendar
3. Create an event in said group calendar
4. Add an e-mail address to invitees
5. Add an Nextcloud user to invitees
6. Add event reminder notification e.g. 5 minutes before event

Expected behavior

.

Installation method

No response

Operating system

No response

PHP engine version

No response

Web server

No response

Database engine version

No response

Is this bug present after an update or on a fresh install?

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

No response

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

.

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[CarlSchwan]

Possibly related #34465

[dzatoah]

Definitely related to: nextcloud/calendar#4400

[gohrner]

Maybe related to #22500 ? (Or the other way around.)

[komoricodrutz]

Hi,
Issue seems to still be there
I have 2 instances of nextcloud, one is 25.0.7, the other is 27.0.2 - for testing before implementation.
I have the same (yahoo) account set up as the "system mail" account and the same (gmail) account set up in the mail app (v2.2.6 on the 25.0.7 instance and v3.2.2 on the 26.0.2 instance). Both mail systems work fine, they send mails as they should.
The options to send invitations to attendees, send notifications for events and send reminder notifications are enabled on both instances.
Log from the 25.0.7 instance when trying to reproduce:
`[dav] Error: Swift_TransportException: Expected response code 250 but got code "550", with message "550 Request failed; Mailbox unavailable
" at <>

0. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php line 344
   Swift_Transport_AbstractSmtpTransport->assertResponseCode()
1. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Transport/EsmtpTransport.php line 305
   Swift_Transport_AbstractSmtpTransport->executeCommand()
2. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php line 406
   Swift_Transport_EsmtpTransport->executeCommand()
3. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php line 502
   Swift_Transport_AbstractSmtpTransport->streamMessage()
4. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php line 518
   Swift_Transport_AbstractSmtpTransport->doMailTransaction()
5. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php line 206
   Swift_Transport_AbstractSmtpTransport->sendTo()
6. /var/www/nextcloud/3rdparty/swiftmailer/swiftmailer/lib/classes/Swift/Mailer.php line 71
   Swift_Transport_AbstractSmtpTransport->send()
7. /var/www/nextcloud/lib/private/Mail/Mailer.php line 191
   Swift_Mailer->send()
8. /var/www/nextcloud/apps/dav/lib/CalDAV/Schedule/IMipPlugin.php line 290
   OC\Mail\Mailer->send()
9. /var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
   OCA\DAV\CalDAV\Schedule\IMipPlugin->schedule()
10. /var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Schedule/Plugin.php line 350
    Sabre\DAV\Server->emit()
11. /var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Schedule/Plugin.php line 627
    Sabre\CalDAV\Schedule\Plugin->deliver()
12. /var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Schedule/Plugin.php line 337
    Sabre\CalDAV\Schedule\Plugin->processICalendarChange()
13. /var/www/nextcloud/apps/dav/lib/CalDAV/Schedule/Plugin.php line 162
    Sabre\CalDAV\Schedule\Plugin->calendarObjectChange()
14. /var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    OCA\DAV\CalDAV\Schedule\Plugin->calendarObjectChange()
15. /var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php line 897
    Sabre\DAV\Server->emit()
16. /var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php line 766
    Sabre\CalDAV\Plugin->validateICalendar()
17. /var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\CalDAV\Plugin->beforeCreateFile()
18. /var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 1094
    Sabre\DAV\Server->emit()
19. /var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php line 504
    Sabre\DAV\Server->createFile()
20. /var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\DAV\CorePlugin->httpPut()
21. /var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 472
    Sabre\DAV\Server->emit()
22. /var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 253
    Sabre\DAV\Server->invokeMethod()
23. /var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 321
    Sabre\DAV\Server->start()
24. /var/www/nextcloud/apps/dav/lib/Server.php line 360
    Sabre\DAV\Server->exec()
25. /var/www/nextcloud/apps/dav/appinfo/v2/remote.php line 35
    OCA\DAV\Server->exec()
26. /var/www/nextcloud/remote.php line 172
    require_once("/var/www/nextcl ... p")

PUT /remote.php/dav/calendars/myuser/personal/38108168-4171-4A8C-B2FC-5639A8D0F7C4.ics
from xxx.xxx.xxx.xxx by myuser at 2023-06-20T14:52:57+00:00`

Log from 26.0.2 instance when trying to reproduce:
`[dav] Error: Unable to deliver message to invitee@company.com

PUT /remote.php/dav/calendars/myuser/personal/1F5F1257-B2B9-481C-A28F-B3748EEB9C9E.ics
from xxx.xxx.xxx.xxx by myuser at 2023-06-20T14:57:33+00:00`
A lot less verbose, although the log reader app is installed

Cheers!

[meichthys]

Just for reference, this still seems to be an issue in Nextcloud 28.0.1 and Calendar v4.6.3
Perhaps the Email Notification option for calendar events should be removed from the UI until this is fixed. It is quite confusing to users.

[ChildLearningClub]

I get email notifications reminders for a calendar that I have, but that same calendar shared with others does not send out the email notification reminders that I have set for the events to their emails. I used the impersonate tool to verify that the calendar events and event reminders are all set correctly as well as their emails.

Edit: I see that my issue is probably related to #22441 which is still open.

Edit 2: No, wait, they do also have edit rights.

[matthias480]

A Little update from my side.

I think we should separate reminder notifications and invitations:

Invitations

@dzatoah wrote: "What should happen: Organizer and invitee get an invitation".

Why should the organizer get an invitation? He/she is the organizer.
At least with Nextcloud 30.0.6, the organizer doesn't get an invitation, which is the expected behaviour in my opinion.

As far as I could see (Nextcloud 30.0.6) invitations work correctly. No matter if the calendar is private or shared, the invitee receives the invitation.

Reminders

The double reminder problem should already be fixed.

@dzatoah wrote:"The reminder is not sent e.g. 5 minutes before but only at the time of the appointment." as well as "reminder notifications are sent only at exact appointment time".

Reminders are not sent at the time of the appointment unless such a reminder has been configured.
But I could reproduce that sometimes the reminder is not sent although the cron job has been running. Then, the reminder is sent on the next cron run. And since your cron job probably runs every 5 minutes, it was sent at the time of the appointment in your case.
The reason for this is explained in #50868

As far as I can tell, this issue can be closed after #50867 and #50868.