You have the possibilities:
You can create your own subusers with "user config & operation control" (you see this link when you are logged in).
A subuser can send you as many files as he wants.
This one-time upload key is an URL you have to give to your communication partner.
To use public upload the fexmaster has to set in /home/fex/lib/fex.ph the public recipients. Example:
@public_recipients = ($admin,'firstname.lastname@example.org');Afterwards one can use http://YOURFEXSERVER/pup
You may test it.