In order to improve the display of the chat history (e-mail traffic) with the customer, it would make sense not only to display the direction of the e-mails via a small icon, but also to fill the timeline from the left and right with incoming and outgoing e-mails, analogous to a chat behaviour with incoming/outgoing e-mails. 

Here, the incoming emails are visible on the left side & the outgoing emails are arranged on the right of the timeline control. 

Furthermore, it would be useful to separate the individual activity types and their respective status values in the timeline by colour, so that they can be better distinguished from each other.

(For example, grey colour background for notes / orange colour background for incoming emails/....).