For those who are frustrated by this, if you can, please show others that there are other options (just like you have done with DuckDuckGo) and switch to any of these (listing only those that are cheap enough to have multiple mailboxes without spending several hundred dollars a year):
1. Posteo.de
2. Mailbox.org
3. Tutanota.com
4. Protonmail.ch
I know some people can run their own setup. The above are for people who cannot or do not want to do it.
I've heard many people say good things about Fastmail, and I'm sure its worth the praise it gets. But I personally don't recommend it because it gets very expensive if you need more than a couple of mailboxes. The services I listed, at least Posteo and Mailbox, are significantly cheaper for those who need separate mailboxes (not aliases on a single account). I moved from Gmail/Yahoo more than a year ago for just two of my primary mailboxes (one personal and one shared) and it costs me a fraction of what a single mailbox on Fastmail would.
1. Posteo.de
2. Mailbox.org
3. Tutanota.com
4. Protonmail.ch
I know some people can run their own setup. The above are for people who cannot or do not want to do it.