Popa3d supports virtual domains separated by IP. This patch allows for separation by an extended username, in the form of username@domain, supplied by the client.
The popa3d-vname changelog
Apply the patch, enable virtual and name-based virtual support in params.h. Create the VIRTUAL_HOME_PATH/VNAME_MAP file in the format "domain:directory". Note that the directory in the map file is relative to VIRTUAL_HOME_PATH.