  We focus on post-asymptotic giant branch (post-AGB) binaries and study the
interaction between the different components of these complex systems. These
components comprise the post-AGB primary, a main sequence secondary, a
circumbinary disk, as well as a fast bipolar outflow (jet) launched by the
companion. We obtained well-sampled time series of high resolution optical
spectra over the last decade and these spectra provide the basis of our study.
The jet is detected in absorption, at superior conjunction, when the line of
sight towards the primary goes through the bipolar cone. Our spectral time
series scan the jets during orbital motion. Our spatio-kinematic model is
constrained by these dynamical spectra. We complement this with a
radiative-transfer model in which the Balmer series are used to derive total
mass-loss rates in the jets. The jets are found to be wide and display an
angle-dependent density structure with a dense and slower outer region near the
jet cone and a fast inner part along the jet symmetry axes. The deprojected
outflow velocities confirm that the companions are main sequence companions.
The total mass-loss rates are large (10^{-8} and 10^{-5}\,solar mass per year),
from which we can infer that the mass-accretion rates onto the companion star
must be high as well. The circumbinary disk is likely the main source for the
accretion disk around the companion. All systems with full disks that start
near the sublimation radius show jets, whereas for systems with evolved
transition disks, this lowers to a detection rate of 50%. Objects without an
infrared excess do not show jets. We conclude that jet creation in post-AGB
binaries is a mainstream process. The interaction between the circumbinary
disks and the central binary provide the needed accretion flow, but the
presence of a circumbinary disk does not seem to be the only prerequisite to
launch a jet.
