Email, phone, text an angry ex can make life miserable if you think you need to respond to every irrational situation he/she creates. You can avoid a lot of problems by setting boundaries about what is proper communication and when you will and will not communicate.
It is within your legal right to insist that communication be via email and, only regarding certain situations. If you are co-parenting with an angry ex, then limit communication to email and only when it concerns child related issues. If your spouse abuses this form of communication then refuse to communicate.
You DO NOT have to communicate with someone who is irrational, refuses to negotiate an issue with you and is only interested in causing more conflict. If push comes to shove you can tell your ex that you will only communicate via your attorney.
It is within your rights to protect yourself from the emotional harm caused by an ex who can't or won't behave rationally.