Fun fact: if you change the subject to a reply in Outlook (the desktop client; not sure about 365) it will automatically start a new thread. This feature was a

Fun fact: if you change the subject to a reply in Outlook (the desktop client; not sure about 365) it will automatically start a new thread. This feature was added because MS found that the "reply to last e-mail from intended recipients" was a common way for people to compose new e-mails.