I hope asking for advice does not violate any rules here.
I am a power email user and pull from about seven (7) email accounts. I have Incredimail, Thunderbird and emClient. All seem to have limitations you would expect from a free email program, although I am using the paid version of emClient. I AM NOT LOOKING FOR A FREE EMAIL PROGRAM, but all of my searches bring up FREE - FREE - FREE.
I am assuming here, but I have to conclude there are some $$$ email programs that offer very sophisticated features that can handle substantial amounts of data without bogging down.
I am running an i7, with 16gb and Windows 7 x64.