Two additional complications make asynchronous communication (email) contentious and inefficient.
First, the participants have to remember the past discussion amidst all of the other thoughts and discussions they have had in between the replies possibly forgetting key pieces.
Second, the amount of data transfer is lower than synchronous communication (phone, face-to-face) so the participants will mentally fill in gaps and sometimes they are filled incorrectly such as thinking someone is angry.
Maybe the interpretation of the response by the receiver is a Rorschach test.