I have issues with notifications, both pop-up and email, arriving later than scheduled which is obviously very frustrating. For today I had setup an event for 9 am with a 15 minute ahead notification by email, but this email only arrived at 9:04, nearly 20 minutes overdue. Looking into the email headers I find instances for received at 8:45:08 but also at 9:04:08.

Received: from system12.eu.zeptomail.net (192.168.136.3 [192.168.136.3]) by mx.zoho.eu
    with SMTPS id 1726124648001829.1321491952413; Thu, 12 Sep 2024 09:04:08 +0200 (CEST)
Received: by mx.zoho.eu with SMTPS id 172612350854382.32763373247826;
    Thu, 12 Sep 2024 08:45:08 +0200 (CEST)