Fixed WooCommerce emails going to spam

I have both Contact Form 7 and WooCommerce on a client’s site. They use Office365 for email. Clients were successfully receiving CF7 emails to their inboxes, but WooCommerce order notifications were being marked as spam. No amount of “not spam” box-ticking could change this, because it was happening before Office actually saw the email.
Installing and configuring this plugin to use SMTP with SendGrid was the ticket. So easy!