title_body: epubcheck error: mimetype entry missing or not the first in archive
upvoted_answer: This error can occur when the mimetype is compressed inside the epub zip file. What can be done is to create a zip file with only the mimetype file inside but with no compression. 
  
  You can do that with 7-Zip setting the Compression level to Store. 
  
  In Linux, you can also do that with the terminal command:
  
  zip -0 file.epub mimetype
  
  
  Then drag and drop the META-INF and OEBPS folders to the file.zip and change the extension to .epub, as usual. With the Linux terminal you can use this command line instead:
  
  zip -9 -r file.epub META-INF OEBPS