sanitize()
  Sanitize (rename attachment filenames) an email.
  
  This scanners is a realscanner, which can be used to sanitize
  email. It means all attachments are renamed to safe names.
  For example "filename.exe" will be renamed to "filename-exe".
  
  WARNING! This scanner is in BETA stage! Id don't conform to RFC 2183!
  
  Usage: sanitize(insert='-',extensions='[a-z0-9]{3}')
  
  Where: insert is a string, which can be inserted for sanitized attachments
         extensions is an regular expressios to find