You should restore a back up that you took of your site prior to the accidental upgrade. :)
There has been 31 releases between 3.6 and 3.9.9 where something like 3.7 alone introduced 700 improvements including structural changes to the database for things like Custom Fields. 3.8 and 3.9 have been preparing Joomla for compatibility with Joomla 4 with some ...
You shouldn't modify core files. Create a contact plugin with onSubmitContact event. Basic example to catch unique emails:
defined('_JEXEC') or die;
class PlgContactEmails extends CMSPlugin
public function onSubmitContact(&$contact, &$data)
I agree with Irata but there may be a simpler solution without having to roll back to Joomla 3.6.
Depending on which template you are using, and depending on whether there were custom changes to the template CSS file or a separate custom CSS file, you may be able to fix the alignment problems by reverting back to the original CSS file that came with the ...
As one commenter suggested, try clearing your browser cache and the Joomla cache and see if that fixes the problem (also try restarting your browser and restart your Internet modem). If that doesn't fix the problem, then open the Chrome console when in the backend (press F12 and then click on console in your browser), and see which files are returning a 404. ...
If you use the ACYMail extension on your site you could use its notification configuration to send a an email to whoever you like, including a list of addresses. You would need to set it up for a new user to auto subscribe to a list, a dummy list if you like, just to trigger the notification on registration/subscription.
An additional part of the solution ...
This sends a private message (including email notification) to all super users.
// Include classes.
JModelLegacy::addIncludePath(JPATH_ADMINISTRATOR . '/components/com_messages/models', 'MessagesModel');
JTable::addIncludePath(JPATH_ADMINISTRATOR . '/components/com_messages/tables');
// Get the model.
$model = JModelLegacy::getInstance('Message', '...
To expand/refine Sharky's answer, you can set up your new/basic database table with this structure:
CREATE TABLE IF NOT EXISTS `#__plg_contact_emails` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`email` varchar(255) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `email` (`email`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
By setting email as a UNIQUE key, you can ...