I view the fact that the d-i couldn't obtain a security update package to be
a defect in the Debian security package distribution chain. If 'apt-get
update' finds that a security update package is available and the d-i wants
to install that package, then 'apt-get update' must be able to download that
package. Which package do I file a bug report against?
There is no defect in the security package distribution chain. mutt is
not part of the Xfce or standard utilities tasks. The installer had no
business attempting to install it.