Your contact form says sent. Where is the email?

Check whether the form accepted it

Submit from the public page, ideally while signed out. Note the exact message shown after submission. Check whether a required field, spam check or upload stops the request before it gets accepted.

If the form keeps a submission record, look for your test. Some forms do not store entries, and adding storage changes what customer information you retain. A missing record is only useful evidence if that form is supposed to create one.

WordPress makes a specific distinction here: a successful return from wp_mail() means the sending method processed the request without reporting an error. It does not establish delivery to the recipient. A form may base its success message on that earlier step.

Source: WordPress: wp_mail() delivery caveat

Follow the message through the sending service

Find the test in the mail provider or sending service log, if you have access. Record the message ID and status. "Queued", "accepted", "deferred" and "bounced" describe different stages; ask the provider what its status means if the label is unclear.

If there's no sending attempt, check the recipient setting and how the website sends mail. If there is a bounce, keep the error text for whoever supports the setup. If the receiving server accepted the message, look at quarantine, junk folders, mailbox rules and forwarding next.

Try a second mailbox you control as a comparison. Delivery there narrows the investigation, but it does not prove that the first mailbox is broken or that every customer will receive a reply.

Use a sender address the website can send from

Check the From address and Reply-To separately. For example, the website might send from website@example.co.uk, with the visitor address in Reply-To. Your mail provider must authorise the chosen sending setup.

Contact Form 7 specifically requires the From address to belong to the website domain. Its documentation also explains where additional mail headers are configured. Other form systems have their own settings, so follow the documentation for the one you use.

I wouldn't put the visitor's Gmail address in From just because it makes the email look convenient. Ask whoever manages the website to set the headers correctly and test where the Reply button actually goes.

Source: Contact Form 7: setting up mail

Ask for the authentication result

SPF, DKIM and DMARC help receiving services assess mail sent using your domain. Google publishes authentication requirements for mail sent to personal Gmail accounts, with additional requirements for bulk senders. The relevant settings depend on who sends your mail.

Ask your provider to check the actual test message and the domain records together. Avoid copying a DNS record from another business or adding an extra SPF record without checking the existing configuration. Your normal mailbox, form service and invoicing system may all send differently.

Authentication is one part of delivery. A passing result does not guarantee inbox placement, and a new SMTP plugin will not resolve every mailbox rule or wrong recipient address.

Source: Google: email sender guidelines

Finish with a received enquiry and a working reply

Repeat the public form submission after the change. Check the message arrives, all fields are readable and replying reaches the test sender. Include any attachment or confirmation email that customers depend on.

Keep the fault, fix and test result in a short support note. Repeat the check after a hosting move, mail-provider change or form replacement. If enquiries matter to the business, give someone responsibility for checking that route regularly.