Outlook 2016 Email not Indexing (The protocol handler Mapi16 cannot be loaded)


There are epic threads on the internet of users upgrading to Office 2016 and finding that Outlook 2016 email is no longer indexing. Windows Search logs the following error in Event Viewer:

The protocol handler Mapi16 cannot be loaded. Error description: (HRESULT : 0x80004005).

I've tried ALL the common suspects:

  • Rebuild Index
  • Reinstall Office
  • Remove and Re-add Outlook from Index Sources
  • Remove and Re-add Outlook Profile
  • We're already running Office 2016 x32

Removing Outlook from the index and using Unindexed search is acceptable as a very short term fix, but I need the "The protocol handler Mapi16 cannot be loaded." error fixed permanently.

At present this is happening on approx 50% of the workstations we upgrade to Office 2016 (Click-to-Run) and they're all running Win10 with all patches.

asked on Super User Feb 23, 2016 by Dom • edited Nov 1, 2016 by MJH

8 Answers


I've been struggling with the very same problem for the past few days.

It turns out it was related to the "HKCU\Software\Classes\VirtualStore" branch of the registry. It contained a few entries in the "MACHINE\SOFTWARE\Microsoft\Office\ClickToRun" subtree, so it was hiding the real "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\ClickToRun" subtree.

After removing the whole "HKCU\Software\Classes\VirtualStore\MACHINE" subtree and restarting the "Windows Search" service, the error disappeared and the indexing started working again.

This is the site that helped me in finding the solution : https://www.win-10-forum.de/office/87414-outlook-2016-office-365-betriebssystem-momentan-ausfuehren-anwendung-konfi.html

answered on Super User Feb 5, 2019 by Sdrik

Tentative Fix (just waiting for reproducibility).

Open Indexing Options and note the number of items in the index. Edit Environment Variables and add to the path:

x32 - C:\Program Files\Microsoft Office\root\Office16\

or x64 - C:\Program Files (x86)\Microsoft Office\root\Office16\

Reboot, Open Indexing Options, note the items in the index, Open Outlook, Indexer starts working on items.

Seems Indexer needs Office in the %Path% in order to open the required files for MAPI16.

Note: On machines where Office 2016 installs correctly, the above path variable is not required, so it doesn't really fix the issue properly, but it does solve the problem in a reasonable manner.

answered on Super User Feb 24, 2016 by Dom

I had this same issue and turns out the cause was adobe pdf pro add in. The add in does not install with office 2016 however it was inherited with office 2013. Disabling the add in then unchecking outlook from advanced. close outlook. rebuild index, checking then allowed indexing to occur again.

answered on Super User May 12, 2016 by nemy

I had the same problem and I was using Office 2016 Small Business that was preinstalled on my Dell laptop. I removed Office entirely via the control panel and after that I used the removal tool from support.office.com. After that, I renamed all folders named 'Outlook' or 'Office' in the AppData subfolder of my profile to make sure the new installation did not reuse them. I reinstalled Office 2016 x64 by downloading it from Office.com. Now all my e-mail is indexed.

answered on Super User Dec 24, 2016 by Jorrit Schippers

This is what I got from a case from Microsoft; Adding the path (#4) was what worked for me. Win 10/64; Office 2016 Pro Plus /32

  1. Open file explorer -> C:\Windows\ProgramFiles

    • look for scanpst.exe.
    • Close outlook and run the tool
  2. https://support.office.com/en-us/article/Outlook-search-stops-working-after-updating-to-build-7870-2020-and-higher-0bcf0b06-320d-40c3-8cf0-7e3df90793ed?ui=en-US&rs=en-US&ad=US

  3. Check for Windows Updates

  4. On the affected machine

    1. Go to Start > System
    2. Click Advanced System Settings
    3. Go to Advanced tab > Environment Variables > System Variables
    4. From the list, select Path
    5. Click Edit
    6. Check to see if the location of the MAPI protocol handler (mapiph.dll) is there. By default, it will be C:\Program Files\Microsoft Office\Root\Office16, as shown below. Notice that you can find mapiph.dll in this folder. REBOOT.
    7. If not, add the path to the value, with a semicolon separated. And click OK to save the change.
  5. If only 1 users affected, please try to recreate the profile.

  6. Follow steps from this link https://blogs.technet.microsoft.com/csstwplatform/2010/07/29/desktop-search-event-3083-window-search-mapi2handler-1-cannot-be-loaded

Also, a tech had added Reg. Key: Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Search DisableServerAssistedSearch DWORD value =1
I do not believe this was necessary, it seemed to be the path of the MAPI protocol handler (mapiph.dll) that resolved it. After a REBOOT.

answered on Super User Jan 27, 2018 by Gary P • edited Jan 27, 2018 by Arjan

Problem was Dixed December 2018 and occured again in January 2019 with Outlook 2016 version 1812. in Cache Mode

Extending path seems not to work for me, happend on Dell Image of Windows 10 updated to 1809 current Patchlevel as of 24.1.2019

What we figured out so far: Problem seems to happen in the Bridge between Windows Search x64 and Outlook mapi x32.

Quick Work Arround: Set Outlok Cache mode to not load all data, then you can search via Server by clicking on the search more line.

answered on Super User Jan 24, 2019 by Michael Mössler

I had this problem on all brand new PCs (win10 20H2 x64). For initial setup I removed the preinstalled O365 (in diff languages) with the o15-ctrremove.diagcab, and here the problems starts:

1. In CONTROL PANEL a void "MAIL (OUTLOOK 2016)" icon
Delete the key



2. MAPI 16 (HRESULT : 0x8007007e)



and change the value

C:\Program Files\Microsoft Office\root\Office16\Interceptor.dll



restart pc, now windows searh gives (HRESULT : 0x800700c1)

Delete the modified keys



Last: remove from windows search the wrong context.

Close outlook,

Restart the PC and voilà! Indexing running in al my PCs!

answered on Super User Feb 23, 2021 by NoRemorse

installing 64 bit office solved this issue for me, i think it has to do with the windows search data file going above 2 GB which 32 bit office cannot handle.

[update 2017-04-06] just to clarify the issue seems to be with the windows search file in ProgramData\Microsoft\Search\Data\Applications\Windows, it seems that when this reaches 2 GB the indexing of emails on 32 bit office stops working. this also explains why when the search files are deleted search starts working again for a short period of time.

answered on Super User Apr 5, 2017 by Mo_AB • edited Apr 6, 2017 by Mo_AB

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