It indeed looks like Outlook does not respect WinSCP preference for copying.
Please consider reporting this to Microsoft.
Until they fix it, you can configure WinSCP to disallow moving files by running it once like this:

https://winscp.net/eng/docs/rawconfig#dddisablemove

Hi Martin

Thank you for your fast reply. The screen shot is attached to this post.

Please post a screenshot of this screen:
https://winscp.net/eng/docs/ui_pref_dragdrop

When dragging and dropping from the WinSCP client to a message in Outlook the file gets moved from the source instead of copying the file to the message. It is somewhat counterintuitive for me when the default behaviour is a copy when dragging from WinSCP to a local folder on Windows.

1. Is this behaviour intentionally?
   
2. Is it possible to change this behaviour in the settings? I am aware that you can force it to copy by holding down Control but is possible to make it the default behaviour?
   

We would like to avoid removing files unintentionally from the remote site.

Best regards Morten

Version of WinSCP: 6.1.1
Windows 10 Enterprise 22H2
Transfer protocol: SFTP
The behaviour is the same in both commander and explorer.