I use Gmail to manage four separate accounts. You can set filters that label each message based on sender, or any search really. For example to:main@gmail.com

I use Gmail to manage four separate accounts. You can set filters that label each message based on sender, or any search really. For example to:main@gmail.com gets labeled and color coded. You can set up multiple inboxes for your accounts. Also it's easy to switch between accounts when replying, to reply from a different address for example. Gmail is just too good for me not to use it, but use whatever works for you.