How do I ask a question on the forums?
Do NOT use TITLE to post whole, long question.
above is just a plain text file regardless of the file extension (*XLS).
Excel can read properly formatted XML files; if you can successfully produce one.
"set markup html on entmap off" might help.
SQL*Plus HTML markup is quite stupid, even more problematic if your data actually have something like HTML tags / entities.
Also, I wonder SQL*Plus HTML markup works with DBMS_OUTPUT.