POPFile uses certain ports by default. These ports may conflict with other software packages running on your machine. You can easily change the defaults to a non-conflicting port by using a commandline option when your startup POPFile.
By default, POPFile listens on port 110 for POP3 connections from your mail client. Some systems require superuser privileges to access ports below 1024, in which case, your option is to either run POPFile from root or change the listen port to a port higher than 1023, for example, 1110.
By default, POPFile's UI listens on port 8080 for http connections from a browser. If you are already running a piece of software that also uses 8080, you'll need to change POPFile to use a different port, for example, perhaps to 9090.
Should you find anything in the documentation that is incomplete, unclear, outdated or just plain wrong, please let us know and leave a note in the Documentation Forum.