Microsoft Outlook is part of the Microsoft Office Suite and it acts as the de facto email client for Windows 10 users.

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However, even a program created by a giant like Microsoft isn’t immune to the occasional bugs in the system.

Such would be the case with Microsoft Outlook, as some users state that they have encountered an error message when using it.

I am getting the following message:
The custom form cannot be opened. Outlook will use an Outlook form instead. The form required to view this message cannot be displayed. Contact your administrator.
This usually happens when I view a Sent email for the Calendar sync to my cell phone. I have tried to fix this with the standard methods of resetting the Forms and / or deleting the Form cache. This does not fix the problem for long.

If you are also encountering this error message, follow this step-by-step guide for a solution to your problem.

What can I do if Outlook can’t open a custom form?

1. Check if Microsoft Outlook item uses a correct Form

  1. Go to the navigation pane
  2. Locate the folder where you want to create a new item
  3. Right-click it and choose Properties from the context menu
    • In the pop-up dialog box, under the General tab, you can see its form in When posting to this folder, use: 
    • You should know that the form:
      • for emails it is IPM.Post,
      • for calendar items it is IPM.Appointment.

If this doesn’t work, proceed to the next solution listed below.

2. Try to manually clear form cache

  1. Navigate  to:
    • C:Users%username%AppDataLocalMicrosoftFORMS
  2. Delete all items in the folder
    • It would be a good idea to back up it before you delete it
  3. Check if the issue persists

outlook the custom form cannot be opened clear form cache
If this method doesn’t work either, you should check the integrity of your Microsoft Office install

3. Open Microsoft Outlook in Safe Mode

3.1. Press and hold the CTRL key to open an Office application
  1. Go to Microsoft Outlook‘s shortcut icon
  2. Press and hold the CTRL key and double-click the  shortcut
  3. When a window appears asking if you want to start the application in Safe Mode, click Yes 

3.2. Use the /safe option to open an Office application

  1. Press Windows + R
  2. Type in outlook /safe, and click OK

outlook the custom form cannot be opened safe mode

4. Uninstall any third-party add-ins

  1. Press Windows + R
  2. Type in control.exe
  3. Go to Programs and Features
  4. Click Uninstall a Program
  5. Look for the add-in in the list
  6. Select it and click Remove

If none of the methods listed above work, you could also try repairing your Office Installation or reinstalling it altogether.

Do you also receive this error message when using Microsoft Outlook?

Do you know and extra solution we haven’t covered?

Please let us know in the comments section below.

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