Up until the macOS Sierra update, I was able to do the following, which I used quite a lot:

  • Start writing an email in Outlook for Mac or in Mail.app.
  • Select a file in Finder that I want to attach to the email.
  • Drag the file to Mail.app (or Outlook) Dock icon.
  • Hover over the Dock icon until the icon flashes a couple of times and then shows the open application windows. You can press the Space bar to speed up the process of showing the application windows.
  • Drop the file into the email window that I opened in the first step.

This has worked fine for years, up until the macOS Sierra update. With Sierra, the app icon in the Dock flashes once or twice and then nothing happens at all.

The settings described in this question also no longer seem to be in Sierra - I can't find them in the Finder Preferences. It looks like this has been moved to Preferences > Accessibility > Mouse & Trackpad, although it does not help.

Dragging files into other application windows (this does not only affect Finder and email) has become a lot more difficult due to this.

Is this a known bug, or is there a workaround that allows to use the above process again for this use case?

  • I don't use the feature often, but I just tried it again and it seems to be working fine for me, so I don't think Sierra has broken it on purpose…
    – grg
    Nov 9, 2016 at 8:50
  • It sometimes works for me once, but then not a second time. I was able to get it to work once after a killall Dock, but then it didn't work a second time.
    – nwinkler
    Nov 9, 2016 at 9:23
  • I can confirm that on 10.12.2 Beta (16C41b) dragging from finder lets say to Mail.app dock icon which will show all open Mail windows (including the new email you're composing) and then holding it for 2 seconds on that outgoing email window will attach that file to that email, Since I currently only have the Beta installed I cannot confirm whether it's a bug or not but it for sure seems to be working down the road.
    – Pinchus G.
    Nov 9, 2016 at 12:11
  • Thanks for the response - does it work multiple times? Like I said, I can currently get it to work the first time, but not after that.
    – nwinkler
    Nov 9, 2016 at 12:12

1 Answer 1


I have just upgraded to Sierra and I am experiencing exactly the same problem, and not only with Outlook. I hope this bug will be fixed in the next release of Sierra.

In the meantime, immediately after beggining dragging I press F9 to show Mission Control and select the target window. Most times, this works.

  • Just tried this, pressing F9 works - it shows all of the open applications and windows and you can select the open email. Thanks!
    – nwinkler
    Nov 25, 2016 at 14:20
  • I'm now using macOS 10.12.4, and the issue has gone away. With this OS version, I can drag the file to the application item in the Dock, wait for the app's open windows to show, and the drag it to one of the windows.
    – nwinkler
    Apr 20, 2017 at 14:20

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