Definitely correct stuff...
URGENT! Please attatch our next life and your public key and return to us within the next 7 days! YOUR LIFE IS IN DANGER! There should be a paper in the bin with the keys written on them titled Cvb #S3 Cfy. Return it to the building north of the one on the stamp.
Based on the hint,
Executing that produces
bwHpGyJe, which leads to https://pastebin.com/bwHpGyJe, which contains an RSA public/private key pair...
Other notes and observations...
The stamp appears to be
based off this stock photo:
Except that it has been squared off, and
has been made partially greyscale. The saturated/desaturated regions create these shapes:
Not sure how much information you can compress into an 8x7 grid, but it's likely important (possibly also related to the game of life, see below). Of course it's also plausibly just an artifact from whichever stock image site OP nabbed the image from initially (there's a different watermark in the centre to the shutterstock one I showed above, but I can't quite make out what it says).
Probably less relevant, but
the image on the stamp is of Château de Gien, in France. The body text says to deliver our message to "the building North of the one on the stamp", but looking at google maps, there's little of obvious interest to the north of Gien Castle.
Finally, commenters below have noted that the image in the top left
is a glider from Conway's Game of Life, which is possibly hinted at in the body text ("our next life"). It also may relate to the grid layout of colours on the stamp, though at the very least running that configuration doesn't seem to do anything special... Of course the glider is also a common hacker emblem, so it may just be thematic.