Hybrid Messaging Addressing Test Results

 © Copyright: Ben Livson 1998-1999. The Inventor. All rights reserved. United States of America Pending Patent Application Number 09/113,344,
Filing Date: 10 July 1998.

Extending SMTP addressing format user@domain to support postal addressing has been tested against:

  1. Allowed size of the user or local-part. Jonathan B. Postel's August 1982 original SMTP RFC 821 section 4.5.3 states a maximum size of 64 for user. That is, every implementation must be able to receive objects of at least these sizes, but must not send objects larger than these sizes. Use techniques which impose no limits on these objects whenever possible.
  2. Separator characters allowed for the local part.

Significant differences exist in the way vendors implement RFC 821 and 822. These differences are significant when expressing a postal address as the local part of an address.

The differences exist both at the Message User Agent MUA email client and sending Message Transfer Agent MTA levels. The inventor has tested the validity of hybrid messaging by using multiple email clients including Netscape Communicator 4.5 Messenger, Eudora Light 3.0.6, Microsoft Outlook Express 4.72.3110.1, Hotmail, Yahoo Mail, and Netcenter - USA.Net web-clients. The MTAs tested include Microsoft Exchange, HP-UX mail, Hotmail, Yahoo Mail, and Netcenter - USA.Net web-mail.

We believe the above represents a widely used cross-section of MUAs and MTAs. The objective of our testing is to ascertain what seems to work across all MUAs and MTAs and highlight any problems with email interfaces. In contract, the web-browser interface ensures valid syntax including the validity of a postal address. For example, in Australia the postal address has to translate to a valid Delivery Point Identifier and in the USA the address has to translate to a valid Zip Code + 4 (or in future into a 11 digit Zip Code). The web-interface will assist the user in matching and expanding the address into a valid address. Depending on the national postal regulation and technology available, the web-interface may automatically pick the current forwarding address (some 15% of all postal addressees have a forwarding address).

The issues are with postal addressing by email clients. The testing results follow:

The MUAs and MTAs tested all allow a 128-character local-part but most of them fail for any longer sizes. For example, Ben.Livson.Managing.Director.BAL-Consulting-PL.36.Minnamurra.Road.Northbridge.New.South.Wales.NSW.2063.Commonwealth-of-Australia.AU@bal.com.au is a valid address. Note that in this test we have made the address artificially long with redundant information such as Northbridge.New.South.Wales.NSW...Commonwealth-of-Australia as 2063.au automatically translates into the above. In fact, the whole postal address could be replaced by the 8-digit DPID in Australia. A typical example of a US postal address follows:


Here, Beverly.Hills.CA is redundant and already expressed by 90211-3204. The normal length of a postal address is 50-to-100 characters. Users of an email client will have a natural inclination to keep the address as short as possible to avoid excessive typing. User guidelines will significantly reduce typing. Thus, the length of a postal address including salutations, person and company name will rarely be a problem.

A more significant problem relates to separators in a postal address. Dot, hyphen and underscore seem to be always accepted. Constructs in quotes " " with spaces and/or commas, however, are rejected by MUAs such as Outlook Express. Constructs such as special-flags@postal-address@domain are misinterpreted by Outlook Express and Yahoo Mail. The parsing of the first left-hand @ is incorrectly interpreted as the at domain @ symbol. All systems, however, seem to accept a hash # instead.

In summary, the testing was highly successful proving the viability of postal addressing as an extension to the SMTP local-part@domain addressing.