My WordPress site has suddenly stopped sending any transactional or form-generated emails. I rely on Microsoft 365 for all domain mail, so messages should be relayed through that service, yet nothing leaves the server. I need someone to trace the exact break-point—whether it lies in the SMTP authentication, DNS (SPF/DKIM), or a mis-configured plugin—and restore reliable delivery. Once you’ve identified the cause, please implement the fix, test with multiple addresses, and leave clear notes so I understand what was changed. I’m comfortable giving temporary admin and hosting access as soon as we start.