It's a good idea, using the correspondence to tell the story.

I realize it's speculative fiction, but a few things bothered me.

I find it hard to accept that there are still nations in the year 26xx...

There are major technological leaps, that even lead us into immortality, but we are still enemies with each other in nation states? Chinese, Russian, etc.

it would be better to advance that present situation into something different. Like the creation of new countries or nations that combined. or wars that wiped out entire continents. Something that led to the advancement of human countries beyond our current situation.

The fact that people can come back in different bodies, would seem to eliminate any barriers of race, and without a land based country there are no borders, so there would be no country.

The part where the guy asks about women is a random thing. It seems out of place. There needs to be a transition of some kind. Like the guy sees an old film or song that speaks of women and makes him feel the need to ask about them.

The lizards are strange. why are we fighting Chinese while these lizard people are deleting humans? Unless its a picture of our real world.

The war seems to be waged through gaming. It's not clear. Perhaps a larger scene that shows a battle. Follow the rules of science for space combat.

The writing is good. The dialogue and ideas are good. There are just a few things that create questions and caused me to be unable to accept. (Nation states)

I realize this is part 1. So maybe those things are answered in the future parts.

I have trouble reading this style of sci-fi. I like things explained to me. William Gibson's "Neuromancer" was similar, I read most of the book and still had no clue what was going on.