Mail delivery is not the same as form submission
A form may save successfully while the notification email is rejected, filtered or never sent. The website should store the enquiry before attempting email delivery.
This prevents a temporary mail problem from deleting a customer lead.
Sender authentication
SPF, DKIM and DMARC help receiving servers evaluate email legitimacy. Sending a message with the visitor’s address in the From field often causes rejection.
Use a domain mailbox as the sender and place the visitor’s address in Reply-To.
Hosting and PHP mail limits
Shared hosting may restrict the mail function, outbound volume or sender domain. A software update can also change form behaviour.
Use logs and a controlled test message instead of repeatedly submitting the public form.
Spam protection failures
Overly aggressive CAPTCHA, firewall rules or honeypots can block real visitors. Conversely, no rate limiting can cause abuse and provider suspension.
Use layered but proportionate protection: CSRF tokens, a hidden field, rate limits and server-side validation.
A reliable setup
Store the enquiry, display a clear success message, send a notification, and provide an admin view or backup delivery route.
Test the complete path regularly from a real external email address.
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