Fixes or workarounds for recent issues in Outlook for Mac

Last updated: October 2016

Outlook for Mac crashes and slow performance

Apple released macOS Sierra on 9/20. We recommend customers in a workplace or school network configuration do not upgrade to macOS Sierra at this time. This is because some customers are reporting Office 2016 for Mac applications are closing unexpectedly, or crashing, on macOS Sierra. Microsoft is working with Apple to resolve this issue.

To check if your network configuration may be affected,

  1. Go to System Preferences and open Network.

  2. Click on Advanced and go to Proxies.

  3. Check if “Auto Proxy Discovery” or “Automatic Proxy Configuration” is turned on.

Turning off “Auto Proxy Discovery” or “Automatic Proxy Configuration” is a possible workaround, if allowed by your organization’s network configuration. Contact your local network administrator for more information on your network settings.

We will update this content when more information is known, including a fix or additional workaround.

If you are experiencing crashes when trying to send emails, this is caused by the Antidote plugin. To fix the problem, upgrade to the latest version of Antidote by going to Antidote > Help > Check for Upgrades.

Customers report that when they use the new @ feature in the 64-bit release, Outlook crashes.

This issue has been fixed in the latest update for Outlook 2016 for Mac. Use Help > Check for Updates from any of the Office 2016 apps to get updates to the newer build.

Customers report that Outlook 2016 for Mac crashes and returns the error "There is a serious disk error on file".

This issue is fixed in builds 15.26, released on 9/13, and later. Please update to the latest build by going to Help > Check for Updates from any of the Office 2016 apps.

Outlook for Mac issues affecting email message, attachments, and other features

When using Outlook 2016 for Mac 64-bit (version 15.25 or later) with the Cisco Web-Ex add-in installed and enabled, the Cisco WebEx add-in button no longer appears on the Home tab on the ribbon.

Cisco WebEx button on the Home tab of the ribbon on Outlook 2016 for Mac

This is a known compatibility issue. To fix this issue, you can download the WebEx Productivity Tools version 31.5.1 or later from For more information on supported versions, go to WebEx Productivity Tools Support (WBS31).

To confirm which version is currently installed on your machine, run the following code from the Terminal:

/usr/libexec/plistbuddy -c 'Print CFBundleVersion' /Library/Application\

When replying to an email message or creating a new one containing an email signature, you receive the following error message:

"Some of the files in this web page are not in the expected location. Do you want to download them anyway? If your sure the Web page is a trusted source, click Yes."

Our engineering team is currently working on a fix for this issue. We'll post back with more information when a fix is released out to our customers.

In Outlook for Mac 15.22 you may notice that the Emacs-style keybindings no longer work properly. We apologize for any inconvenience this issue has caused and want to assure you that the Outlook team is working on a fix. We will update this article when the issue is resolved.

You may not be able to connect Outlook 2016 for Mac to an Exchange server after you install 15.23 update for Mac.

This issues has been fixed in update 15.24 that was released on July 12th. Please install the update to resolve this issue. Use Help > Check for Updates from any of the Office 2016 apps to get updates to the newer build.

When composing emails, automatic language detection is not working in the new Word-based editor for Outlook 2016 for Mac (versions 15.20 and later). Our engineering team is working on a fix but in the meantime, you can you can assign a shortcut key for quickly changing languages in the new Edit > Language settings menu as shown below.

Outlook 2016 for Mac Language settings under Edit menu

Outlook 2016 for Mac Keyboard Shortcuts settings dialog box

When pasting text and images in the new mail editor for Outlook 2016 for Mac (version 15.20 or later), paste doesn't default to 'Match Destination Formatting.'

We apologize for this inconvenience. Our engineering team is currently working on a fix, but in the meantime, you can use the paste control icon and choose ‘Match Destination Formatting.’

  1. Go to your email message, and select Edit > Paste.

  2. At the bottom of the pasted text you'll see a paste control icon. Click it to reveal your paste options, and choose Match Destination Formatting.

    Paste options when pasting text into Outlook for Mac

    • Keep Source Formatting keeps all of the original formatting and images.

    • Match Destination Formatting changes the font to match what you're using in your message. Images are unchanged.

      Tip: If the font size increases when you paste text into your message, use this paste option to solve the problem.

    • Keep Text Only removes all of the formatting and images and leave only the text.

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