Re: Splitting and encoding of local-parts: some thoughts

Roy Badami <[email protected]> wrote:

> (1) We could encode the whole dequoted localpart in one go.  But then
> we can't use punycode as the ACE, because it could produce multiple
> consecutive dots, and I really don't think we want to go there.

I'm not sure we need to be quite so fearful of quoting, but we should
certainly keep this in mind as we weigh the options.

> (2) We could simply split at dots, and encode using punycode as the
> ACE. ...if dots are commonplace in internationalized localparts, the
> extra ACE prefixes would eat into our length limit.
>
> (3) split at all non-alphanumeric ASCII characters. ...this will eat
> into our length limit further.

Yes, we need to weigh the benefit of being friendly to structured local
part conventions (like user+tag@domain) and the benefit of IDNs copied
into local parts being displayed intelligibly (like user%domain@domain
or listname-return.user=domain@domain) versus the cost of extra ACE
prefixes, and the cost of the extra subdividing step.

> I'd also like to throw a slightly wacky idea out there: if we accept
> that any prefixes and suffixes applied to (or stripped off from)
> e-mail addresses are restricted to ASCII, then it is adequate to
> identify the substring of the localpart from the first non-ASCII
> character to the last non-ASCII character, and encode and mark that in
> some way.
>
> Is it reasonable to restrict users of localpart suffixes (delimited by
> plus or minus) to restrict their suffixes to ASCII characters?

I would think that anyone who wants to use the user+tag convention, and
wants to use non-ASCII characters in the user part, probably also wants
to use non-ASCII characters in the tag part.

AMC