When emails are tracked on a case timeline the entire email thread gets imported each time, rather than just the first message of an email. This causes obvious problems when the email thread starts to have many replies. As in each reply to each email gets imported as a new activity on the timeline every time.

My suggestion is one of two things:

1. A delimiter. Something that lets Dynamics know that the first message in each reply is the newest email and only that email should be inserted. I've used the string "From:" which works well 99.99% of the time. When the words "From:" are seen on an activity to truncate the rest.

2. Move the arrow that expands an activity.

https://imgur.com/a/Q94pANd

When the arrow is clicked it stays at the bottom of the activity box. If this arrow is used to expand an email activity that contains 40 replies in order to collapse the activity you must scroll down through all the email to collapse it. If the arrow were in the top part of the gui for the activity it could be expanded and collapsed without any scrolling at all.