You may receive this error whilst using the Skype for Business client:
To resolve this issue, please follow these steps:
You may require IT assistance to perform these steps.
1) Run REGEDIT and goto:
Right-click and create a new key called Outlook64Bridge
2) Right-click Outlook64Bridge and create two keys under it DLLPath and DLLPathEx
Find the 32 bit version of the file MAPI32.dll and assign the whole qualified pathname to each key, mine were:
3) Go back to the root key name and show the default client as Outlook64Bridge
NB - Editing the Registry can cause irreversible damage to your computer. Please follow these instructions with caution. Smart Hosted Solutions Ltd provide no guarantee or warranty for changes you make to the registry.