bt email migration

Its cool if you have unlimited data, and no sub accounts and an outlook express programme to download the emails and archive them if you have sub accounts - bt are being particularly obtuse and so far i have emailed and talked to their help centre three times and not received some of my sub account passwords - my fault for setting them up each year but i still want the old email folder info ok if you have unlimited bband but not if you are on pay as you go - a large email account can be 1Gb to sort.