Outlook pop-up when CompoundFileAnalyzer is in execution

Hi all,

in my company we are experimenting a strange behaviour on some notebooks,

Windows version and KB installed are the same in the whole environment, obviusly with the delay of SCCM patching performed thru VPN during covid time.

During the day the pop-up:

"Either there is no default mail client or the current mail client cannot fulfill the messaging request. Please run Microsoft Outlook and set it as the default mail client." 

appears to some users, and opening the task manager the process ongoing is the CompounFileAnalyzer.

Pop-up may be forced to appear on affected PCs starting a manul backup.

 

Windows 10 Enterprise 64x 1909 18363.1443

Office 365 ver 2008 13127.21348

Connected Backup 8.1.1.2

Is a tricky situation due doesn't affect all the PCs, it was never seen before, and the google community refers usualy to the MAPI registry key or to the preview handler of outlook.

Anyone ever had similar issue?