The Full-Screen Interruption
macOS includes a multitasking feature called Split View, which allows you to run two applications side-by-side in full screen. In a somewhat controversial design choice, Apple deeply integrated this feature with the native Mail app. If you have the Mail app running in full screen, and you click on an email to compose a reply or open a new message window, macOS will often automatically split your screen, forcing the compose window to take up half your monitor alongside your inbox.
For users who prefer a standard floating compose window—allowing them to drag the draft around, reference other applications, or quickly check multiple emails while writing—this automatic Split View behavior is highly restrictive and annoying. You can force Mail to use standard floating windows instead.
How to Stop Automatic Split View in Mail
You can change the full-screen behavior directly in the Mail application preferences.
- Open the Mail app on your Mac.
- In the top menu bar, click on Mail and select Settings… (or Preferences).
- In the popup window, click on the General tab at the top.
- Look down the list for the section regarding full-screen behavior.
- Find the checkbox labelled Prefer opening messages in split view when in full screen.
- Uncheck the box.
Now, even if you are using the Mail app in full-screen mode, clicking “Compose” or replying to a message will open a standard, floating draft window on top of your inbox, giving you back control over your workspace layout.