D. Crocker Mail Addresses1

Structure and Scope of Structure and Scope of Internet Mail AddressesInternet Mail Addresses

<address> = <local> “@” <domain><domain> = <dpart> *( “.” <dpart>)

“@” and “.” are global syntax <domain> is global semantic <local> is globally opaque

<local> Local to cited domain – local MTA(s) and local MUA(s) No one else’s business!

D. Crocker Mail Addresses2

Address HandlingAddress Handling

Sender Copy an opaque string Senders do not construct

addresses! Source/Relay MTAs

Move message to <domain>

<local> is opaque; ie., ignorant of local structure

Target Domain Interpret <local> <local> might follow local

structuring conventions

Multiple MX References

Distributed MTA Must share <local>

syntax and semantics Forward to master

MTA Same as

“intermediate”

D. Crocker Mail Addresses3

<local> Conventions<local> Conventions

Mailbox assignment User vs. System chosen Login-specific, or not

Structuring Function of target MTA May include MUA

Encoding No global standards (well, almost none) May be layers of encoding May have significantly different presentation style

D. Crocker Mail Addresses4

IEA GoalsIEA Goals

Expand permitted range of characters Global enhancement

Must not break installed baseMust not break local conventions(!)

Approach: Reserve “unused” bitsOutside current ASCII range, orSpecial ASCII-based “framing”

D. Crocker Mail Addresses5

TidbitsTidbits

Unicode representation vs. encoding UTF-8 is merely one of several encodings ACE is merely another encoding <Local> strings are short

Intermediary MTAs do not interpret <local> Using non-ASCII bits changes this

Adoption times New, endpoint-only protocol: 3+ years Existing protocol: 10+ years “transition” is forever Existing multi-step infrastructure is worse

D. Crocker Mail Addresses6

<local> Enhancement<local> Enhancement

Must respect local conventionsWithout knowing them

Create Unicode segmentsFlag start and flag end

IDN could rely on “.”, to flag end IEA cannot must define global segment

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