Completely talking out of my ass here but those electrons making up the density of matter in inter-stellar space, could they be what is causing CMB radiation?

Completely talking out of my ass here but those electrons making up the density of matter in inter-stellar space, could they be what is causing CMB radiation? Seeing as energy is never lost, they just bounce around interstellar space until caught up in a heliosphere of a star system. Either way I love how the Voyager probes are literally giving us first real impressions of the universe beyond theories.