Managing personal Outlook.com account settings, security, and privacy
Hi ,
I'm Dyari. Thanks for reaching out. I will be happy to assist you in this regard.
Unfortunately, it can’t be cancelled directly from our side once it’s in progress. Could you confirm whether you’re using Outlook on the web or the desktop app, so I can give you exact steps?
In the meantime, check your mailbox storage, delete or archive unneeded items to free up space. If the export is creating a PST file in Outlook, you can close Outlook and remove the export job from the Import/Export Wizard to stop further processing.