Does our newsletter system work in a way that would allow us to edit this out after sending it?

I'm sure there is some queue and that it takes seconds or minutes to send out the newsletter. Either our system saves a copy to send when that queue is formed or it keeps referring back and it's possible that if the queue takes awhile it would pick up edits.

I think we should edit these after the fact to not look as much like newsletters. So the question is do we need to wait until we are sure all the emails went out or can we do it as soon as we've pressed send?