Show HN: Create your own private mail service in 15 seconds
blog.kimeralive.com
blog.kimeralive.com
This could be one, but it seem such a hassle, mailing and explaining et cetera.
You can use your own domain, just not automatically..yet. There are several aspects to consider, DKIM & SPF would have to be handled by the customer and so it is tricky to guarantee the same results we do now.