The contact form on a published Web Presnece Builder (WPB) site cannot send any email message.
It may be caused by the fact that SMTP service is disabled on the host where the problem WPB site is published. Contact forms are using mail function from the server where the site is published, and therefore it is crucial that the SMTP service is turned on on the server.
Enable the SMTP service on the host where the problem WPB site is published.
Note: It is possible to use external mail server, but for Windows publishings server only.
Add additional PHP directives
smtp_port in domain's
<external_smtp_server> - host name or IP address of the SMTP server PHP should use for mail sent with the mail() function;
port_number> - number of the port to connect to the server specified with the SMTP setting when sending mail with mail(); defaults to 25.