[dns-operations] TLD(s) for private use

Viktor Dukhovni ietf-dane at dukhovni.org
Wed Sep 6 18:55:44 UTC 2017

> On Sep 6, 2017, at 5:28 AM, James Stevens <James.Stevens at jrcs.co.uk> wrote:
> Or is the correct procedure to be using something like "data.invalid."?

I've been using the "invalid" and "localhost" TLDs for various internal purposes for over a decade.

* address.invalid  -- decorates domain-less bare-localpart addresses from external senders

* discard.invalid  -- blackhole rewrite domain

* example.com.localhost -- Special-use names (typically MX records) served by the local
                           resolver, visible on just the one host (often a border MTA).


I try to make these reasonably self descriptive, to avoid any confusion.  This has
worked well.  In your case, "externally.invalid" could be a viable parent domain
for private-use, but a real domain is cheap enough, and a better choice in most


More information about the dns-operations mailing list