Hi roadcykler, yes, it's a bug. A team of developers worked on this over the weekend and developed a fix that is in testing this week in the Nightly release. Firefox 58 probably won't get that update for 1-3 weeks... When you get back to Firefox 58, these are the three workarounds I'm aware of (other than using zoom in the message to temporarily fix the mouse behavior in that one message, e.g., Ctrl+ or Ctrl-): '''(1) Use the Reading pane''' If you have a wide display, you could try using the Reading pane on the right side of the Inbox. <img src="https://prod-cdn.sumo.mozilla.net/uploads/images/2018-01-26-17-23-07-0dc34b.png" width="500"> ---- '''(2) Switch to the Outlook beta layout''' There is a "Try the beta" switch above the Inbox. You'll be able to switch back equally easily if you don't like it. <img src="https://prod-cdn.sumo.mozilla.net/uploads/images/2018-01-26-17-28-32-0960eb.png" width="400"> ---- '''(3) Revert to the older layout engine for the site''' (A) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk. (B) In the search box above the list, type or paste '''stylo''' and pause while the list is filtered (C) Double-click the '''layout.css.stylo-blocklist.enabled''' preference to switch the value from false to true (D) Double-click the '''layout.css.stylo-blocklist.blocked_domains''' preference and set the value to '''live''.''com''' and click OK. (In the unlikely event that you already had one or more sites listed add ''',live''.''com''' to the list.) Then exit/quit Firefox and start it up again to make the change effective.