Internet address syntax (and semantics, for that matter)

[Barry Margolin]

In article <4270 at buengc.BU.EDU> bph at buengc.bu.edu (Blair P. Houghton) writes:
>In article <29725 at news.Think.COM> barmar at think.COM (Barry Margolin) writes:
>>In article <2274 at ttardis.UUCP> jcf3703 at ttardis.UUCP (chap flack) writes:
>>>cfctech!sharkey!chenry at carleton.edu.
>>	cfctech! ((sharkey!chenry) @carlton.edu)
>The way a bang-at address is interpreted (is it really undefined)
>is to send to the at-machine, then start down the bang-path.

It really is undefined.  Many systems even parse it differently
depending on the source.  For instance, if the address foo!bar at baz
comes in from the UUCP mail server the "!" is parsed first; if the
same address were to come from an SMTP mailer server the "@" would be
parsed first.

>It's obvious that our friend only has to use the address "chenry at carleton",
>since the mail got through carleton to cfctech, and then to sharkey,
>which bounced it.

That's a possibility.  In fact, that was my first thought.  But I
assumed that he would know whether his own machine knew how to route
SMTP addresses automatically, and wouldn't have bothered with the UUCP
addressing if he didn't need it.

>What I'd like to know is, why not just fix mailers to accept the address as
>
>	"carleton to cfctech to..."
>
>instead of all this !%@.

That wouldn't be any easier than getting them to all have smart
routers so users could all just say "user at domain"; they both involve
fixing thousands of mailers.  And during the transition period (five
to ten years), you'll have the problem of THREE different mail address
formats instead of just two.  The general direction of mail routing is
away from requiring users to specify routes explicitly (e.g. the MX
records in the domain system); computers are supposed to be good at
figuring out those kinds of things.

Barry Margolin
Thinking Machines Corp.

barmar at think.com
{uunet,harvard}!think!barmar