Why is my Magento store not sending any emails?

In most cases it’s one of four things: (1) the email sending cron group or message-queue consumers aren’t running, so async emails just queue up; (2) the mail transport is broken, PHP mail() blocked or an SMTP relay misconfigured; (3) a fatal in the email template stops the render; or (4) Sales Emails is switched off in config. We trace the path from sales_email config to the MTA and find the exact break point, usually within a few hours.