Are you asking if shortnames play a role into the internet mail address? No.
This posting does not share any specific information for one to explain something. It makes it hard to give advice because R6 is going to rely on configuration document, domain documents, etc.
R6 has change things within the server configuration.
It may be helpful to reveiw R6 in how it formulates an email address. I have had posting on this subject within the forum.
Subject: As long as there is only one “John” at domain.com, the mail will be delivered to him.
The router searches the ($Users) view for names. You can change this behaviour on you configuration document by selecting Fullname only…
Address lookup
Specifies how the Router searches the Domino Directory to determine the Notes recipient of an inbound Internet message. Choose one:
Fullname then Local Part - (default) The Router first searches the Domino Directory for a match for the full Internet address (localpart@domain.com). If no match is found, it searches the directory again, looking for a match for the local part of the address only.
Fullname only - The Router searches the Domino Directory for full Internet addresses only. For example, it searches for ‘user@domain.com’ but not for ‘user.’ If an exact match is not found and the domain suffix is equivalent to an Internet domain alias defined in the Global domain document, a secondary search is performed using the domain suffix of the primary Internet domain.
Local Part only - The Router searches the Domino Directory for a match of the local part of the Internet address, that is, the part before the @ symbol. Local part matching matches periods and underscores in the address with spaces in the directory.
Subject: RE: As long as there is only one “John” at domain.com, the mail will be delivered to him.
this is only true if there is not an email address already defined on the person document. I have made a post describing how the domino server derives an email address for its users.