Steps to reproduce the issue

Simpler Install site with 5.4.0-beta1 and send test email.

Original procedure:

• Install site with 5.4.0-beta1 with disabled Automated Updates
• Install 'Alpha Update Server' plugin from 45540
• Enable 'Log Almost Everything' and 'Debug System'
• Enable Automated Updates
• After Automated Update check log file administrator/logs/everything.php

Expected result

The log messages correspond to the system behaviour.
I do not know the internals. Perhaps there are multiple attempts to send the email on different ways?
The log entries should also show that the e-mail was sent successfully. If this is not possible, then at least the attempt. The entries currently read as if it was not possible to send the e-mail

Actual result

The Log messages show only email errors, but the email was sent successfully.

2025-08-21T16:22:33+00:00       INFO 52.14.131.139      update  Update to version 5.4.113 is complete.
2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: Sending with mail()
2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: Sendmail path: /usr/sbin/sendmail -t -i
2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: Envelope sender:
2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: To: "joomla-test@xxx.de" <joomla-test@xxx.de>
2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: Subject: =?utf-8?Q?Joomla!_updated_successfully_at_joomla-test.heikol?=^M
 =?utf-8?Q?.de_=E2=80=93_https://joomla-test.heikol.de/?=
2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: Headers: Date: Thu, 21 Aug 2025 16:22:33 +0000^M
From: "joomla-test.heikol.de" <joomla-test@xxx.de>^M
Message-ID: <DEwZxDD4cnip4jhKYfory2S5P489XvNbIHz0Sjg@joomla-test.heikol.de>^M
MIME-Version: 1.0^M
Content-Type: text/plain; charset=utf-8^M
^M

2025-08-21T16:22:33+00:00       ERROR 52.14.131.139     mail    Error in Mail API: Result: true

The log entries only show errors, even though the e-mail was sent successfully.

System information (as much as possible)

Seen two times today for site joomla-test.heikol.de

Additional comments

This issue may have the lowest priority.