Welcome to the community, @ROSEMONDE! :grinning_face_with_big_eyes: What types of fields are in the data that you’re exporting? Even though you specified UTF-8, it’s possible that something in the data still isn’t “clean.”
Have you opened the CSV file to inspect the data directly? Maybe something in the file will stand out.
You might also try exporting a smaller data set. Perhaps something in a particular record is messing things up.
Another idea is to start from scratch with completely different data. Just throw some random things together in the same general format, export that as a CSV file, and see if Outlook accepts it.
My point here is to run lots and lots of tests to see if you can isolate the problem. Keep notes on what happens in each test so that you can spot possible patterns. The hope is that you can find something that will be an “a ha!” moment and let you know what’s causing the hiccup. Let us know what happens!