[Discuss] box.net

[Tom Metro]

Edward Ned Harvey wrote:
>> I'm not aware of the address extension mechanism being codified in any
>> RFC. (Reference?)
> 
> RFC5233 "subaddressing" is an optional configuration for your MTA.

Close. RFC5233 is about:

   On email systems that allow for 'subaddressing' or 'detailed
   addressing' (e.g., "ken+sieve at example.org"), it is sometimes
   desirable to make comparisons against these sub-parts of addresses.
   This document defines an extension to the Sieve Email Filtering
   Language that allows users to compare against the user and detail
   sub-parts of an address.

So this RFC is about using "subaddressing" (I've always heard them
referred to as "extensions") in a Sieve filter. (Sieve filters are a way
of managing mail filtering rules that run on your mail server instead of
your client.)

It refers to "subaddressing" as some existing convention, and implies it
is defined elsewhere, but interestingly provides no link or footnote to
where it is defined.

It does reference RFC2822 (an update of the classic RFC822) as the place
where email addresses are defined. RFC2822 doesn't contain
"subaddressing" and only mentions "extension" in the context of
Multipurpose Internet Mail Extensions (MIME).

So while I haven't specifically looked for an RFC covering address
extensions, these two RFCs would likely reference one, if it existed.

Consider also that the extension separator character is changeable via
configuration parameter in most MTAs (at least Sendmail and Postfix),
further suggesting that the "+" character itself isn't a universal
standard. (On my own Postfix installation I have it set to "-".)

 -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/