Seeing a form on a page confirms that the interface loads. A useful check also confirms that the intended recipient receives the message.
Submit a short test with a unique phrase in the subject or body. Note the time and the confirmation shown on screen. Ask the recipient to check the inbox and spam folder, then verify the sender and reply address in the received message.
Test missing required fields separately so visitors receive clear instructions when a submission fails. Record the destination mailbox and the person who can change it. Repeat the delivery check after switching hosting or email providers.