Why does this last line print twice?

Question

This can be deleted if it should not be here, I'm new.

I'm trying to take the username and domain of an email address and print it as the following:

domain, username

However, when I run the following code:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

void parseTheEmail(string email, string &username, string &domain){
   username = "";
   domain = "";
   int atPosition = email.find('@');
   username = email.substr(0, atPosition);
   domain = email.substr(atPosition+1, -1);

   return;
}

int main(){
   string email, username, domain;
   string filename;
   cout << "Please enter a filename> ";
   cin >> filename;
   cout << endl;
   ifstream files;
   files.open(filename);

   while(!files.eof()){
      files >> email;
      parseTheEmail(email, username, domain);
      cout << domain << ", " << username << endl;
   }
   files.close();

   return 0;
}

It prints the last email out twice and I can't figure out why. For example, if I had:

stanford.edu, john
stack.com, mike
google.com, bob

It would print google.com, bob twice.

Why is this?