January 5, 2021, update for Outlook 2016 (KB4493166)

Applies to: Outlook 2016

This article describes update 4493166 for Microsoft Outlook 2016 that was released on January 5, 2021.

Be aware that the update in the Microsoft Download Center applies to the Microsoft Installer (.msi)-based edition of Office 2016. It doesn't apply to the Office 2016 Click-to-Run editions, such as Microsoft Office 365 Home (see What version of Office am I using?).

Improvements and fixes

This update fixes the following issues:

  • Fixes an issue that blocks users from providing justification text when they override a policy.
  • Fixes an issue that causes users to experience occasional crashes while they use Outlook.
  • Fixes an issue that causes the headers of Chinese email messages to be unreadable when you reply to or forward messages.

This update also contains the following improvement:

Adds a registry key that enables customers to disable file time inclusion for attachments in IDataObject operations (for example, by dragging and dropping an attachment from the clipboard into an email message).

  • Path: HKEY_CURRENT_USER \SOFTWARE\Microsoft\Office\16.0\Outlook\Attachments
  • Value name: IncludeFileTimesInDataObject
  • Value type: REG_DWORD
  • Value data:
    • 1 (default): File times are included.
    • 0: File times are excluded.

​​​​​Note If there is no Attachments subfolder under HKEY_CURRENT_USER \SOFTWARE\Microsoft\Office\16.0\Outlook, you have to create it.

How to download and install the update

Microsoft Update

Use Microsoft Update to automatically download and install the update.

Download Center

This update is also available for manual download and installation from the Microsoft Download Center.

If you're not sure which platform (32-bit or 64-bit) you're running, see Am I running 32-bit or 64-bit Office? Additionally, see more information about how to download Microsoft support files.

Virus-scan claim

Microsoft scanned this file for viruses by using the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to it.

Update information


To apply this update, you must have Microsoft Office 2016 installed.

Restart information

You may have to restart the computer after you install this update.

More information

How to uninstall this update

Windows 10

  1. Go to Start, enter View Installed Updates in the Search Windows box, and then press Enter.

  2. In the list of updates, locate and select KB4493166, and then select Uninstall.

Windows 8 and Windows 8.1

  1. Swipe in from the right edge of the screen, and then select Search. If you're using a mouse, point to the lower-right corner of the screen, and then select Search.

  2. Enter windows update, select Windows Update, and then select Installed Updates.

  3. In the list of updates, locate and select KB4493166, and then select Uninstall.

Windows 7

  1. Go to Start, enter Run, and then select Run.

  2. Enter Appwiz.cpl, and then select OK.

  3. Select View installed updates.

  4. In the list of updates, locate and select KB4493166, and then select Uninstall.

File information

The English (United States) version of this software update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). The dates and times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and times may change when you perform certain operations on the files.


outlook-x-none.msp file information
File identifier File name File version File size Date Time
Contab32.dll Contab32.dll 16.0.5104.1000 156,512 15-Dec-2020 18:26
Dlgsetp.dll Dlgsetp.dll 16.0.5002.1000 112,960 15-Dec-2020 18:26
Emablt32.dll Emablt32.dll 16.0.5104.1000 134,016 15-Dec-2020 18:26
Envelope.dll Envelope.dll 16.0.5104.1000 191,352 15-Dec-2020 18:26
Mapiph.dll Mapiph.dll 16.0.4999.1000 334,960 15-Dec-2020 18:26
Mapir.dll_1033 Mapir.dll 16.0.4723.1000 1,280,712 15-Dec-2020 18:25
Mimedir.dll Mimedir.dll 16.0.5104.1000 450,352 15-Dec-2020 18:26
Olmapi32.dll Olmapi32.dll 16.0.5104.1000 4,823,920 15-Dec-2020 18:26
Omsmain.dll Omsmain.dll 16.0.5095.1000 755,056 15-Dec-2020 18:26
Omsxp32.dll Omsxp32.dll 16.0.5095.1000 263,072 15-Dec-2020 18:26
Outllibr.dll_1033 Outllibr.dll 16.0.4966.1000 7,498,576 15-Dec-2020 18:25
Outlmime.dll Outlmime.dll 16.0.5104.1000 615,816 15-Dec-2020 18:26
Outlook.exe Outlook.exe 16.0.5110.1000 23,298,880 16-Dec-2020 20:14
Outlook.hol_1033 Outlook.hol Not applicable 1,812,658 15-Dec-2020 18:25
Outlph.dll Outlph.dll 16.0.5071.1000 360,344 15-Dec-2020 18:26
Outlvba.dll Outlvba.dll 16.0.5104.1000 78,704 15-Dec-2020 18:26
Pstprx32.dll Pstprx32.dll 16.0.5104.1000 1,404,232 15-Dec-2020 18:26
Rm.dll Rm.dll 16.0.5095.1000 92,496 15-Dec-2020 18:26
Scnpst32.dll Scnpst32.dll 16.0.5104.1000 424,400 15-Dec-2020 18:26
Scnpst64.dll Scnpst64.dll 16.0.5002.1000 436,888 15-Dec-2020 18:26
Scnpst64c.dll Scnpst64c.dll 16.0.5002.1000 635,360 15-Dec-2020 18:26


outlook-x-none.msp file information
File identifier File name File version File size Date Time
Contab32.dll Contab32.dll 16.0.5104.1000 204,136 15-Dec-2020 18:48
Dlgsetp.dll Dlgsetp.dll 16.0.5095.1000 141,152 15-Dec-2020 18:48
Emablt32.dll Emablt32.dll 16.0.5104.1000 168,832 15-Dec-2020 18:48
Envelope.dll Envelope.dll 16.0.5104.1000 250,752 15-Dec-2020 18:48
Mapiph.dll Mapiph.dll 16.0.4999.1000 483,448 15-Dec-2020 18:48
Mapir.dll_1033 Mapir.dll 16.0.4723.1000 1,280,744 15-Dec-2020 18:48
Mimedir.dll Mimedir.dll 16.0.5104.1000 606,008 15-Dec-2020 18:48
Olappt.fae Olappt.fae 16.0.4687.1000 134,464 15-Dec-2020 18:48
Olmapi32.dll Olmapi32.dll 16.0.5104.1000 6,668,152 15-Dec-2020 18:48
Omsmain.dll Omsmain.dll 16.0.5095.1000 1,005,944 15-Dec-2020 18:48
Omsxp32.dll Omsxp32.dll 16.0.5095.1000 353,696 15-Dec-2020 18:48
Outllibr.dll_1033 Outllibr.dll 16.0.4966.1000 7,498,568 15-Dec-2020 18:48
Outlmime.dll Outlmime.dll 16.0.5104.1000 788,360 15-Dec-2020 18:48
Outlook.exe Outlook.exe 16.0.5110.1000 35,112,768 16-Dec-2020 20:13
Outlook.hol_1033 Outlook.hol Not applicable 1,812,658 15-Dec-2020 18:48
Outlph.dll Outlph.dll 16.0.5071.1000 430,992 15-Dec-2020 18:48
Outlvba.dll Outlvba.dll 16.0.5104.1000 100,208 15-Dec-2020 18:48
Pstprx32.dll Pstprx32.dll 16.0.5104.1000 2,593,096 15-Dec-2020 18:48
Recall.dll Recall.dll 16.0.4759.1000 76,088 15-Dec-2020 18:48
Rm.dll Rm.dll 16.0.5095.1000 112,440 15-Dec-2020 18:48
Scnpst32.dll Scnpst32.dll 16.0.5002.1000 530,360 15-Dec-2020 18:48
Scnpst64.dll Scnpst64.dll 16.0.5002.1000 533,448 15-Dec-2020 18:48
Scnpst64c.dll Scnpst64c.dll 16.0.5104.1000 731,624 15-Dec-2020 18:48


Learn about the standard terminology that is used to describe Microsoft software updates. The Office System TechCenter contains the latest administrative updates and strategic deployment resources for all versions of Office.