Indeed. I thought about a blog post how to configure haproxy to proxy SMTP to mailinator and stay undetectable.

But Mailinator's use case has morphed over the years. It's now used as a tool for QA and UAT testing now a great deal. That use case has spawned private domains and API access.

Same thought process goes toward services that wish to ban it, if they really want to, that's their business.

(You can of course sign-up for a Mailinator account using a Mailinator email)