title: Regular expression for strings not containing brackets
body: <p>I am trying to edit my .procmailrc file to get rid of junk.</p>
  
  <p>The account is from the CS departments at my school, all the emails within the department have subjects with brackets in them for instance:</p>
  
  <blockquote>
    <p>[Majors] Some Subject</p>
  </blockquote>
  
  <p>or:</p>
  
  <blockquote>
    <p>[Undergrads] Another Subject</p>
  </blockquote>
  
  <p>I get a LOT of spam not caught by the filters but almost all of them don't include brackets. I want to move these emails into a folder for spam but can't figure out the REGEX. Any regex masters out there that can help?</p>