Nope, most is Chromium overhead and a bug that the Chromium team are working on. (300mb is maximum, when it's just running and doesn't run into any of the bugs it consumes around 170mb on my computer) I expect Chromium to use less and less memory as time progresses, so RAM will probably decrease in the future.

Inbox seems to use about 200mb right now. However this is within Chrome and runs several additional plugins.

When I use mutt I doubt it goes over 20mb.

28mb

But then it is mutt running inside a screen session in an xterm.

Screen is using 4m, and the largest xterm open is using 2.4m. So even adding in screen and xterm overhead that's still only 34.4mb.