ICANN opens up Pandora's Box of new TLDs

Tony Finch dot at dotat.at
Tue Jul 1 12:10:29 CDT 2008


On Mon, 30 Jun 2008, Jay R. Ashworth wrote:
> On Mon, Jun 30, 2008 at 06:47:30PM +0100, Tony Finch wrote:
> >
> > Trailing dots in email addresses are a syntax error.
>
> In fact, Mutt (1.2.5) permits the trailing dot, and delivers the mail,
> and all the intervening MTAs (I only tested local mail on my machine,
> running Postfix) let the message through -- it came through apparently
> having been rewritten by Postfix to lose the trailing dot; there was an
> X-Original-To header.

Postfix corrects many syntax errors rather than rejecting erroneous
messages.

> Tony: what authority were you depending on for your assertion, and in
> which context do you make it?

It has been true of all internet email addresses since before dots were
introduced into host names.

RFC 2821 section 4.1.2 Command Argument Syntax

      Domain = (sub-domain 1*("." sub-domain)) / address-literal
      sub-domain = Let-dig [Ldh-str]
      Let-dig = ALPHA / DIGIT
      Ldh-str = *( ALPHA / DIGIT / "-" ) Let-dig

Note that this does not permit a trailing dot. (It also doesn't permit
single-component domains, but that's due to an editorial mistake.)
Section 4.1.2 of RFC 821 also does not permit trailing dots.

RFC 2822 section 3.4.1 Addr-spec specification

domain          =       dot-atom / domain-literal / obs-domain
dot-atom        =       [CFWS] dot-atom-text [CFWS]
dot-atom-text   =       1*atext *("." 1*atext)

This also does not permit trailing dots. RFC 822 section 6 is similar.
See also RFC 733, which allows no dots at all.

Tony.
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