Thanks for posting your question on Justanswer.com, a global paid independent support site.My Name is ***** ***** I will be assisting you today. First of all, I want to clear that, we are not Microsoft support, so please do not give any negative rating for the changes Microsoft makes to Hotmail while upgrading to Outlook.com.
Whereas Hotmail provided users with a chronological view of ever email they had received, Outlook.com groups together correspondents that have been sent by the same contact into an ongoing thread, making it difficult for users to pick out individual messages.
It means all the message from a user will be in a group when you click the latest message from that particular contact, you will see the list of the messages which they have send you earlier. Please let me know, if you need any further help otherwise please remember to give a positive rating as that is the only way I am compensated for my time and effort.