qmail doesn't honor the mbox/maildir USE flags. The postfix ebuild does this, so I think it'd be the right thing to do in qmail too. The mbox/maildir flags aren't mutually exclusive, and since most programs support to have both simultaneously the question becomes which one takes precedence if both are enabled. In the original qmail package Mailbox delivery is the default. In addition, which one (mbox/maildir) is used if neither is specified (?), shouldn't one of them be in make.defaults, or should it be up to the package to decide? I can think of one reason why qmail doesnt honor the USE flags. Mbox seems to imply delivery to /var/mail/$USER in gentoo, which is not possible to do in defaultdelivery. I think delivery to ~/Mailbox is the right thing to do. Most programs support it and/or use MAIL to find the mailbox. Administrators can also create symbolic links in /var/mail for compatability if they really need it. Reproducible: Always Steps to Reproduce:
how about this as behavoir: if only one is specified, then it takes precedence if both or neither are specified, display a warning and use Maildir. The major question is for mbox, /var/spool/mail/$USER or ~/Mailbox ? I can provide both right out of the box, but only ~/Mailbox will support per-user procmail rules. with my new system as of -r14, you could simply change an item in a configuration file, and restart qmail-send. All of the configurations will be in place, and selectable with a simple flip in my configuration files.
actually, I could do per-user procmail with /var/spool/mail/$USER my concept for delievering to that location will be _pure_ procmail eg qmail-local hands off delivery to procmail. This will require that /etc/procmailrc is set to deliver to the correct location.
~/Mailbox is supported now, just change defaultdelievry to suit your needs.