[Bug]: Nextcloud 28 don't send notification when accept a meeting

[section1]

⚠️ 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 OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Using the calendar app in the web interface when i create a meeting with UserB as guest, the calendar server send the invitation notification...As UserB i go to the calendar app in the web and i accept the meeting the calendar DON'T send the email notification saying that the meeting was accepted. Both users in the same instance.

In version 27.x this works fine. I receive an email when meetings are accepted.

Steps to reproduce

1. Log as UserA to Nextcloud and create a meeting with UserB.
2. Email invitation of the new meeting arrives to UserB
3. Log as UserB in NC and accept that meeting in the calendar.

Expected behavior

An email notification deliver to UserA saying that UserB accepted the meeting.

Installation method

Community Manual installation with Archive

Nextcloud Server version

28

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.1

Web server

Apache (supported)

Database engine version

MariaDB

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

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

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

Configuration report

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "***REMOVED SENSITIVE VALUE***",
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "28.0.1.1",
        "overwrite.cli.url": "***REMOVED SENSITIVE VALUE***",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "skeletondirectory": "",
        "defaultapp": "calendar",
        "session_lifetime": 14400,
        "remember_login_cookie_lifetime": 172800,
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "25"
    }
}

List of activated Apps

Enabled:
  - calendar: 4.6.4
  - circles: 28.0.0-dev
  - cloud_federation_api: 1.11.0
  - contactsinteraction: 1.9.0
  - dav: 1.29.1
  - federatedfilesharing: 1.18.0
  - federation: 1.18.0
  - files: 2.0.0
  - files_trashbin: 1.18.0
  - files_versions: 1.21.0
  - logreader: 2.13.0
  - lookup_server_connector: 1.16.0
  - nextcloud_announcements: 1.17.0
  - notifications: 2.16.0
  - oauth2: 1.16.3
  - password_policy: 1.18.0
  - privacy: 1.12.0
  - provisioning_api: 1.18.0
  - related_resources: 1.3.0
  - serverinfo: 1.18.0
  - settings: 1.10.1
  - systemtags: 1.18.0
  - theming: 2.3.0
  - twofactor_backupcodes: 1.17.0
  - updatenotification: 1.18.0
  - user_ldap: 1.19.0
  - user_status: 1.8.1
  - viewer: 2.2.0
  - workflowengine: 2.10.0
Disabled:
  - activity: 2.20.0 (installed 2.20.0)
  - admin_audit: 1.18.0
  - bruteforcesettings: 2.8.0
  - comments: 1.18.0 (installed 1.18.0)
  - dashboard: 7.8.0 (installed 7.8.0)
  - encryption: 2.16.0
  - files_external: 1.20.0
  - files_pdfviewer: 2.9.0 (installed 2.9.0)
  - files_reminders: 1.1.0 (installed 1.1.0)
  - files_sharing: 1.20.0 (installed 1.20.0)
  - firstrunwizard: 2.17.0 (installed 2.17.0)
  - photos: 2.4.0 (installed 2.4.0)
  - recommendations: 2.0.0 (installed 2.0.0)
  - sharebymail: 1.18.0 (installed 1.18.0)
  - support: 1.11.0 (installed 1.11.0)
  - survey_client: 1.16.0 (installed 1.16.0)
  - suspicious_login: 6.0.0
  - text: 3.9.1 (installed 3.9.1)
  - twofactor_totp: 10.0.0-beta.2
  - weather_status: 1.8.0 (installed 1.8.0)

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[ChristophWurst]

In version 27.x this works fine. I receive an email when meetings are accepted.

I doubt that it is the same workflow. As far as I know Nextcloud never sent replies for accepted invites when the response happened through the HTML button in the invitation email or someone used the Calendar app to respond on web.
Only when someone uses an external client, like Thunderbird, there is a response email.

[section1]

Im doing a test right now with NC 27.1.6 when i accept the event from here:

The userA receive this email notification:

[section1]

Hi i have news ... today i test 27.1.5 and breaks this reply notifications... reading the changelog i see something that maybe it's related to this regression:

title : [stable27] fix(scheduling): don't send iMIP emails to rooms / resources
#41315

Im not sure how to revert this fix in 27.1.5 to see if works reverting this change.
If someone have the steps to do this provide it please so i can test it.
Thanks.

[ChristophWurst]

https://docs.nextcloud.com/server/latest/admin_manual/issues/applying_patch.html#reverting-a-patch

[section1]

many thanks for the link... i will do that and get back with the result... but i append a log that i found relatable.

REDACTED,"user":"My_User","app":"dav","method":"PUT","url":"/remote.php/dav/calendars/My_User/personal/sabredav-1e99337b-5d82-4ba1-8a76-44ef8405d984.ics","message":"Could not find recipient [email protected] as attendee for event with UID f649542e-d4c4-4abb-8a6a-a2ef6f9f5a81","userAgent":"Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:120.0) Gecko/20100101 Firefox/120.0","version":"27.1.5.1","data":{"app":"dav"}}

[section1]

Ok i can confirm that without this patch( https://patch-diff.githubusercontent.com/raw/nextcloud/server/pull/41315.patch ) works as expected... and i see the email send it in the debug logs.

REDACTED,"user":"My_User","app":"core","method":"PUT","url":"/remote.php/dav/calendars/My_User/personal/sabredav-79ac2cc1-4b29-4594-9aa1-d918afa61bca.ics","message":"Sent mail to \"Array\n(\n [[email protected]] => User\n)\n\" with subject \"Re: 13\"","userAgent":"Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:120.0) Gecko/20100101 Firefox/120.0","version":"27.1.5.1","data":{"app":"core"}}

[ChristophWurst]

Thanks for testing @section1!

Could you share the ics of the event you reproduced this with? Redact any sensitive data like your email or the description of the event.

https://docs.nextcloud.com/server/stable/user_manual/en/groupware/calendar.html#edit-duplicate-or-delete-an-event

[ChristophWurst]

We don't need the ICS. This is trivial to reproduce.

1. Create two users with email addresses
2. Log in as user 1
3. Create an event and invite user 2
4. Log in as user 2
5. Accept the event in the web

The reply is sent from user 2 to user 1. User 2 is the attendee. \OCA\DAV\CalDAV\Schedule\IMipService::getCurrentAttendee returns null.