1. The file does not include column headings. Tableau Online assumes that every line in the file represents a user.
2. The file is in UTF-8 format, and includes the byte-order mark (BOM).
3. Character encodings such as BIG-5 have been converted to UTF-8. You can do this by opening the file in a text editor and using the Save As command.
4. If a user name includes an @ character that represents anything other than a domain separator, you need to refer to the symbol using the hexadecimal format:  \0x40 For example, user@fremont@mycompany.com should be user\0x40fremont@mycompany.com