Fix Contact Form Email Delivery

My contact form lives on a shared-hosting site and relies on the basic PHP mail() function. Visitors see the “message sent” confirmation, yet nothing ever reaches my Gmail inbox—spam folder included.

I need you to trace and solve whatever is blocking delivery. Whether it’s a server configuration, missing SPF/DKIM records, or the limitations of PHP mail(), the end goal is simple: every form submission must arrive reliably in Gmail.

Please diagnose the root cause, implement the fix—switching to authenticated SMTP, PHPMailer, or another method if that’s the cleanest path—and show me a successful test message hitting the inbox.