Changing structure of Maildir

[Victor <victor_volpe@xxxxxxxxxx>]

Hello,

This is my current structure of Maildir:
"/mailhome/domains/mydomain.com/user"

How I can change folder structure of Maildir to:
"/mailhome/domains/mydomain.com/u/user" ??

Each user inside of a folder with the initial of the name account.
Examples:
"/mailhome/domains/mydomain.com/u/user"
"/mailhome/domains/mydomain.com/p/postmaster"
"/mailhome/domains/mydomain.com/d/david"

Ps.: I'm using qmail 1.03 + vpopmail 5.4.10 (with mysql)

Thanks very much :-)