no notification but log error

[redncsk]

Steps to reproduce

1. The mail app works normally, but I don't get any notifications in the dashboard or via notifications in the header of Nextcloud
2. Every new incoming email causes an error message in the log instead

Expected behavior

1. When new emails have arrived, they should appear in the ‘Unread emails’ dashboard widget
2. Notification at the top of the bell icon (?)
3. No error messages should appear in the log, please

Actual behavior

Newly arrived emails only appear in the ‘Unread emails’ dashboard widget after the Mail app has been opened. But instead the following error message in the log for the new incoming e-mail:

Zeit : 31.03.2025 - 15:09:04 * IP :xx.xx.xxx.149 * Benutzer :xxxxxxxxx * App :PHP * Methode :POST * URL :/index.php/apps/mail/api/mailboxes/1/sync *
Grund :Undefined array key 191 at /home/html/xxxxxxxx.xxx/_sub/nextcloud/apps/mail/lib/Service/Classification/NewMessagesClassifier.php#92

I hope I have conveyed all the information clearly, as I am still new here. Thanks and best regards

Mail app version

4.3.3

Nextcloud version

31.0.2

Mailserver or service

IMAP

Operating system

Linux 5.4.0-208-generic x86_64

PHP engine version

PHP 8.3

Nextcloud memory caching

No response

Web server

Apache (supported)

Database

MariaDB

Additional info

{
"reqId": "Mgcod8GIxuY4p2Qdy7QO",
"level": 3,
"time": "2025-03-31T14:09:04+00:00",
"remoteAddr": "xx.xx.xx.149",
"user": "xxxxxxxxx",
"app": "PHP",
"method": "POST",
"url": "/index.php/apps/mail/api/mailboxes/1/sync",
"message": "Undefined array key 191 at /home/html/xxxxxxxxx.xxx
/_sub/nextcloud/apps/mail/lib/Service/Classification/NewMessagesClassifier.php#92",
"userAgent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36",
"version": "31.0.2.1",
"data": {
"app": "PHP"
},
"id": "67eaa2542ec7d"
}