Nikolai,

The first value for the port just after "host" was mistakenly typed as "465" here,  in fact it is   also "587" in "settings.php"  like the second port value.

Your config is incorrect. Here're the correct settings:

$CONFIG->emailer_transport = 'smtp';

// $CONFIG->emailer_sendmail_settings = '';

$CONFIG->emailer_smtp_settings = array(
    'name'              => 'localhost.localdomain',
    'host'              => 'ni-chrome.guzelhosting.com',
    //'port'              => 25,
    'connection_class'  => 'login',
    'connection_config' => [
        'username' => 'user',
        'password' => 'pass',
        'ssl'      => 'tls',
        'port'     => '587',
         //'use_complete_quit' => '',
    ],
);

I was wrong in the previuos post. Here's the corrected version:

$CONFIG->emailer_transport = 'smtp';

// $CONFIG->emailer_sendmail_settings = '';

$CONFIG->emailer_smtp_settings = array(
    'name'              => 'localhost.localdomain',
    'host'              => 'ni-chrome.guzelhosting.com',
    'port'              => 25,
    'connection_class'  => 'login',
    'connection_config' => [
        'username' => 'user',
        'password' => 'pass',
        'ssl'      => 'tls',
        'port'     => '587',
         //'use_complete_quit' => '',
    ],
);

You shouldn't comment out the default port (25)

Just Google it.

Try to delete log files from /your_data_directory/logs/html/

Thank you Nikolai. Deleting log files solved the problem.

If this is about Site notifications, have a look at https://github.com/ColdTrick/site_notifications_tools.

This allows you to set a retention period for the notifications, after the retention period the notifications will be removed.

Thanks Jerome! :)