There is no substitute for getting away from the person. When they cannot be avoided, I've found Bill Eddy's techniques really helpful:
https://www.amazon.com/gp/product/B00NMTN0Y4/ref=dbs\_a\_def\_rwt\_hsch\_vapi\_tkin\_p1\_i3
> I also wouldn’t suggest going back to phone calls or not saving communication because you guys may backslide into a more high conflict relationship, whether you have sole custody or not.
Thank you for sharing this problem and being so concerned about your son. I agree with spsrta2967391: For your child's sake, as a wise judge in my area said, 'the one who keeps the old Valentine's cards wins," meaning, keep the proof for now, because it is often true that someone who loses full custody is more likely to be planning on proving how to get custody back than ready to submit to "defeat."
But I also agree that sending an email about "burying the hatchet" (yes, poor choice of words because it could mean "in your skull" instead of "in the ground" so it is setting all of us off a little! just saying) is too soon - and may be perceived as gloating. Instead, step carefully and with sensitivity. I like what someone else said: Use demonstrations of how you will act, and also light emails demonstrating your willingness to share.
Have you read any of Bill Eddy's books on communicating using BIFF (Brief, Informative, Factual, and Friendly)? They help you turn the 7-page email that you may be tempted to respond to with 8 pages, into a few lines responding to just the essentials in a healing way. Of course, I don't presume to know whether you need that sort of thing but many in custody battles have a history of poor communications that CAN be repaired. Amazon: https://smile.amazon.com/Biff-Responses-High-Conflict-Personal-Attacks-ebook/dp/B00NMTN0Y4/ref=tmm_kin_swatch_0?_encoding=UTF8&qid=1609440762&sr=8-5