email from space, I mean in space

Energy requirements wouldn't necessarily have to be as
high as other posters have indicated. If all our
receivers are on earth and the transmission must be
pinpointed to the earth, then yes the signal strength
must be very high at point of origin. If however the
receivers are scattered through the entire solar
system, a much lower power signal can be used to
communicate, as long as the vehicle making the journey
(and transmissions) is not situated directly on a line
between A Cen and a receiver. Reconstructing the
original signal from the ones received by thousands of
antennae outside the orbit of Neptune would be a bit
of a bear, but not an insurmountable task.