What can be then the shortest way, to display historical emails under the history tab?

Its good for collaborating work internally, but for the work with the customers its very imperfect. The easy communication trackability is absolutely missing. Before talking with a supplier or customer, cant create always for tiny or for adiscussion new document to abel to follow and track at the partner form. But i write just cause i eager to see , and use this last missing fuction... Any idea for solving this? But going out for a chatter and making serching what can anybody can done with clerical error.... so its not a way...

You can goto your wall and filter inbox by your partner through advanced search. After filtering you will see all history. It is concept - split the information to help manage it. If you need full history e-mails goto wall. If you need messages about specific document goto document. You can have conversation with partner about:
his contact (document contact), his sales order (document order), his project (document project) and etc. It is different. You will in conext not only with partner but also with specific document! This concept reduces the load on the brain overloaded with information.

I agree that need link to e-mail history from partner form.