WordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. Features include a plugin architecture...
Send a test message and check the recipient address in the form configuration, including any typing errors. Look in the spam folder too. If the form keeps a sending log, check whether the message was processed or an error occurred; an on-page confirmation does not prove delivery to the inbox.
Check the configured sending method. If you use SMTP, verify the server, port, encryption and login details against your email provider’s instructions. Use an authorised address as the sender and put the visitor’s address in the Reply-To field. Also check the SPF and DKIM records against your sending service’s requirements.