http://www.postfix.org/
config in:
/etc/postfix/main.cf
config in:
/etc/postfix/main.cf
\flushleftx(u) = \begin{bmatrix}1 \\ 1 \\ 0 \end{bmatrix} \\y(i) = \begin{bmatrix}0 \\ 1 \\ 0 \end{bmatrix} \\\centering\\\flushleftpreference: p(u,i) = x^\intercal(u) * y(i)\\\centering\\\flushleftmin \sum\limits_{u,i} (r(u,i) - p(u,i))^2 + \lambda (||x(u)||^2 + ||y(i)||^2)