Cybersex...LOL...seems so outrageous and pitiful to me. I can't even imagine. But the mind is very powerful...the mental attraction one can develop to a total stranger online. Must be very unhappy and desperate to do such a thing. I could never go there, but, YES, if one has a partner, that would definitely be a form of infideltly.
As for corresponding with a male, I do that. I have an old highschool sweetheart with whom I've corresponded for many years now. His wife knows of this, and we just update each other on our lives, etc.
I don't consider this infidelity, but i did tell him that we must refrain from romantic references, and we do.
Patty