I use runbox. It costs money, but is affordable. They also take privacy and security seriously, and they take steps to help the environment when possible.
First runbox user I've seen in the wild. +1 for runbox, it has worked great for in the last ~6 years or so.
The 100 aliases you get are very useful. The fact it costs money may be a turn off for many, but I'd personally wouldn't trust a privacy statement from a closed source free service.