I ran a Postfix/Dovecot setup for years and they were both fast, reliable, lightweight, and very flexible. The #dovecot and #postfix channels on Freenode are also tremendously helpful if you are in a pickle. (Full disclosure, I don't run my own mail server anymore except for a few virtual aliases; a good webmail client was the weak link in the chain and Fastmail provides a reliable service with a phenomenal web client at a fair price).
I was using Roudcube, but it was not powerful enough for my needs. The greatest strength of the Fastmail UI are all of the built-in keybindings. There's one for almost every action, indeed, I find it friendlier than the best desktop clients I've used, let alone ones like Gmail or Roudcube.
