Help Center Creating an URL hash
Each domain needs a hash to be sure that the mailhash is been translated from the correct origin. You can do this on domain base, for example www.site.com and www.site.com/files.php will use the same HASH.
Each domain, needs its own hash. You can hash your domain on 'Hash an URL'.
Note:
If you want www.site.com and site.com both to work, you will need to create 2 hashes, one for each domain name.