in vpopmail 5.3.24 vpopbull needs the -f email_file parameter even you just want to generate a list of the mail adresses of a domain. Its not really a bug and it is easy to work around but it makes no sense, so maybe it is possible to change to the earlier behavior that you can run vpopbull -n -V domain to get a list of all email adresses of domain.
cheers andrej
