I have no idea why the Outlook App cant open the XML file. It just loads a blank screen, no errors or messages. Outlook on PC loads it fine. Thanks for the link, I will look into that.

Why the "Outlook App on my iPhone" cannot open the XML log? What does it say? What if you rename the XML log file to .txt?

Note that you can transform the XML log to whatever format you like. For an example, see:
https://winscp.net/eng/docs/logging_xml#parse

I'm using a batch file to run WinSCP to copy changed files from a web server to my local machine.
When I use /xmllog, I get a very small file and it only list the files that were downloaded. This is great, and what i want – but some apps, like the Outlook App on my iPhone, can't open the resulting XML file.

If I switch to using /log, I get a big file (2-5MB) that's quite verbose, even if loglevel is set to -1.

Ideally I'd like to use a universal file type, such as .txt, so that everything can open it – but with the same functional and easy to read "only show files that were downloaded" capability of the XML logging.

I'm sure im doing something wrong, but not sure what, any help or suggestions appreciated....