Notifications for new emails not showing up any more

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

Thunderbird for Android

App version

18.0

Where did you get the app from?

Google Play

Android version

16

Device model

Pixel 7a

Steps to reproduce

1. Configure email accounts to use folder polling (sync) for email retrieval.
2. Make sure that Thunderbird is configured to show notifications for new emails.
3. Make sure that the system settings for notifications are enabled for Thunderbird.
4. Wait for new emails to arrive.
5. Check the Android notifications.

Expected behavior

Notifications should show up when new emails are received.

Actual behavior

There are no notifications from Thunderbird.

Notes:

• Even though there are no system notifications, Thunderbird does show the number of new emails on the unified inbox widget icon.
• This problem only started recently. I think the first version I saw it with was Thunderbird 17.0
• This is not the same as issue #7839 which was also reported by me. That other issue is about receiving the emails. This new issue here happens even when the emails are received.
• I found a similar issue, #10098. But I think this is different since I'm not using push.

Logs

No response

Start by reproducing the issue with folder polling enabled, checking whether new messages appear in the unified inbox widget while Android notifications remain absent. Compare Thunderbird's notification settings with the system notification settings, and verify that the fix restores notifications for newly received emails without relying on push.