I deleted my AcademiaSE profile, and nearly had a heart attack (do-not-reply@stackoverflow.email) with a subject line of "Your profile has been deleted".
Why is this notification sent from an email address that appears to be for another site on the network?
.email
domains. Then we'd need certificates for all of them. And we'd need IPs or aliases for them. And DMARC support. And reputation monitoring. And we'd have to build into the entire system what to send from where. These added up are significantly more than "just buying another domain". Not that it helps much, but I wanted to illustrate the scale of the simple fix implied here...because it's not simple.