Microsoft 365 Shared Mailboxes Disappearing After 30 seconds or a minute

In this post, we will guide you through the steps to configure your registry and fix the disappearing mailbox issue.

Registry Configuration Steps

To solve the disappearing mailbox problem, you'll need to tweak the Windows Registry. Follow these steps below:

1. Open the Registry Editor:

   • Press `Windows + R`, type `regedit`, and hit `Enter`.

     
     

2. Navigate to the Correct Subkey:

   You will be editing one of two subkeys based on your setup:
   

   • `HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\Autodiscover`

     OR

   • `HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\x.0\Outlook\Autodiscover

   
   

3. Create or Modify the DWORD Value:

   
   

   • Check for the entry named `ExcludeLastKnownGoodUrl`. If it is missing, right-click in the right pane, select `New`, then `DWORD (32-bit) Value`, and name it `ExcludeLastKnownGoodUrl`.

   • Set the value to `1`.

   
   

4. Close the Registry Editor and restart Microsoft Outlook for the changes to take effect.

   
   

Reference: https://community.spiceworks.com/t/365-shared-mailboxes-disappear-after-a-minute/785501/11