I'm not sure what P03 is, but it you mean POP3 then you've got a 5-10 split. Gmail does support POP and e-mail forwarding, meaning you can use your own e-mail client such as Outlook or Thunderbird. Yahoo, on the other hand, does not give you that functionality unless you have Yahoo Mail Plus...their paid service. Thus you'll be able to use the client for two accounts, but still have to check Yahoo separately.
In regards to setting the e-mail client up, you can click here for a tutorial on Thunderbird, and here for a guide to using Outlook Express.
Hope this helps,
I have around 4-6 emails that i check on daily. Fire fox's plug-in gmail notifier has helped me save time on which emails to check and which to not. I have gmail and yahoo account and will be getting another one when school starts( a school e-mail account.) Well your probably saying that i should make one account and delete the other ones. Well tell you the truth some of these acounts are shared between people in my family and co-workers. I tryed to use my gmail account in thunderbird but it was too complicated. My question is does g-mail and yahoo even support p03? and if so how can i set them up in a program like thunderbird or outlook.