Laravel SMTP Email Fix

My Laravel 8 site is hosted on Hostinger and has suddenly stopped sending transactional emails. Test messages never leave the server, yet the rest of the application runs fine. I have already generated fresh SMTP credentials; they simply need to be wired in correctly and the send-mail flow confirmed... (Budget: ₹600 - ₹1500 INR, Jobs: cPanel, Debugging, Laravel, Linux, MySQL, PHP, SendGrid, SMTP, Web Development, Web Hosting)