Test of your e-mail configuration

ERROR: Please provide a valid e-mail address in testmail.php.

In case of error, here are some additional steps:

Check the configuration with your IT Admin team.
If you are using GMAIL, please read this article.
The STMP port may be blocked by your organization/server's security policy (firewall, etc.).

When running SELinux, the webserver is blocked by default (it cannot send e-mails or open a network connection). Please consider unblocking it:

                    $ setsebool -P httpd_can_sendmail 1
                    $ setsebool -P httpd_can_network_connect 1

Some e-mail servers (eg Office 360) require to set a valid sender e-mail. Update config/config.php
$config['from_mail'] = 'do.not@reply.me';
Some antivirus block STMP port by default.
Some SMTP server require the application server sending emails (i.e. Jorani) to be whitelisted (on the SMTP server).
Your webhosting company may forbid email functions.
Maybe that the emails are sent but put into SPAM folder.