Surprisingly, Office 365 Exchange + Outlook has this now. https://support.office.com/en-gb/article/like-an-email-message-in-outlook-on-the-web-for-business-cfd

Surprisingly, Office 365 Exchange + Outlook has this now. https://support.office.com/en-gb/article/like-an-email-message-in-outlook-on-the-web-for-business-cfd919a9-7c3e-40ed-a6e6-aabd7d2d2acb https://support.office.com/en-gb/article/like-an-email-messa...