I completely understand where you are coming from. The emails we receive and respond to have a lot of potential lasting consequences both legally and emotionally. It is difficult knowing which ones should be answered and which ones should be left alone. It makes it even more difficult because the response has to be taken in terms of legal consequences and most of us are not lawyers and can't pay a lawyer to help us respond to each email. I am also finding I am getting better at keeping all emotions and feelings out of my responses but even that can convey a sense of coldness. I have to say ~U~ that the emotional drain on things like this can sometimes be overwhelming.
It is absolutely a drain.
For instance, my W asked to shift our schedule for an upcoming weekend. My initial reaction was NO. Why should I put myself out? But I requested she give me some time to consider. I looked at it, figured out I would end up with some more time with the kids at the expense of using up a little bit of my work flexibility, and decided to say OK. I did not feel compelled to say yes or no based on her needs.
Great, right? But it's still exhausting to go through that process. Careful attention to every word. I guess in my case once I have a more formal legal agreement I will feel safer.
And it is frustrating to know if I asked for the same, I would get a hard NO.
Rather than aim for coldness, I aim to keep things business-like. Some of the advice in co-parenting is to use "I feel..." statements, but I think that doesn't work if the other person does not care about how I feel. (similar to validation here). I prefer to remain neutral and calm yet guarded.