On Twitter, Google’s John Mueller said that it does not matter if you write the domain: directive in upper-case or lower-case:
@Marie_Haynes Yes, upper-case or lower-case for that directive is fine.— John Mueller (@JohnMu) 7 January 2015
How to create a disavow links file for Google
The link disinfection tool in SEOprofiler can help you to locate backlinks that have a negative influence on the rankings of your website. The link disinfection tool also creates a disavow links file for you.
If you haven’t done it yet, try SEOprofiler now: