POP mail handles only one account and one server.
Every program has things going for and against it . . .
Free Not a pure e-mail program. Many viruses are designed to propogate through the Outlook Address book. It's convenient to have the list of what is in your inbox refreshed every now and then to let you know that new mail has arrived since you last grabbed it. You can ask the POP program to check your mail every so many minutes. Having the program set to check mail every so often will deny you control of this.