Software or service to consolidate all email addresses?

I am looking for software, freeware or online service that can consolidate all my various personal and client email accounts, from Yahoo, Google, Hotmail into one platform? Any suggestions on what will work, or advice on what you have found that works the best?

 

Try thunderbird its free

 

Thanks for the suggestion! I went ahead and paid the extra money on my Yahoo account, to have the ability to forward those email addresses to Google. I would have preferred to find another way, but that seemed like the best at the time, and I think it was just $15 or maybe $20 for the whole year...