Outlook.exe keeps running after opening .eml or .msg files

[GlSis]

After opening and then closing some .eml or .msg files with Outlook 2019 NOT in execution, the Outlook.exe process continues running in the background, while in the notification area the program icon is indefinitely visible in grey with an X and the words "Outlook will be closed".

Before the problem occurs, in the notification area Outlook shows the message "Folder synchronization by Microsoft Outlook in progress".

Problem encountered: you can no longer open other .eml or .msg files or launch Outlook itself without first terminating the Outlook.exe process.

Solution to avoid the problem: set Outlook in "Offline" mode or have previously launched the program before opening .eml or .msg files.

Failed attempts to solve: disable all plugins, scan all .ost files with SCANPST.EXE.

Any ideas on how to solve definitely ?

[#2]

Anyone ?

[#3]

@GlSis managed to find an answer on this?

[#4]

@Jestallion, no, no definitive solution has been found, except the expedient I indicated in my first post.

The problem occurs even in the latest versions of Outlook 2019 with all updates installed, indicating that Microsoft has not fixed the problem.

[#5]

@GlSis I was able to resolve the issue by disabling the 'Empty the Deleted Items folder when Outlook closes' configuration setting from an Intune configuration profile for Outlook that was being applied to devices. 

Empty the Deleted Items folder when Outlook closes should apply for GPO.