[dns-operations] underscores in domain names

Tony Finch dot at dotat.at
Tue Sep 12 10:13:29 UTC 2017

Jim Reid <jim at rfc1035.com> wrote:
> > On 12 Sep 2017, at 10:19, James Stevens <James.Stevens at jrcs.co.uk> wrote:
> >
> > It would be impossible to disagree - just interesting to see that
> > underscore in public names is astonishingly common - like SRV records,
> > so I assumed underscore was reasonably well supported.
> It is perfectly legal to use underscores in domain names. They can't be
> used in hostnames.

Nor in mail domains :-)

So if you put a _ in a fake TLD, you can't use it for very much ...

f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/  -  I xn--zr8h punycode
German Bight, Humber, Thames, Dover, Wight: West or southwest 5 to 7,
increasing gale 8 or severe gale 9, perhaps storm 10 later. Moderate or rough,
becoming very rough, occasionally high later. Showers, rain later. Good
becoming moderate or poor later.

More information about the dns-operations mailing list