I'm giving my neglected gmail a treat today For Windows users:
  Highly recommended. IMAPSize lets you do things to your IMAP
  email (like [1]#Gmail ) - like back it up to your local
  computer, find large attachments that might be slowing down your
  gmail retrieval, etc.* While you can read emails with it (I
  think), it's strengths are that it handles all the maintenance
  tasks that one might imagine and even some things you might not.
  I've been on Gmail from the Beta days and always wanted to be
  able to back it up.* I've done some manual cleanups but really,
  what I wanted is to back it up into standard text files (.eml or
  .mbox) really easily just in case Gmail one day decides to go
  away.* [because Google does have a bad habit of taking away
  services it gets bored with) and with many years worth of stuff
  shoved in there, it'll be nice to have a local copy. Anyway,
  it's a tool that's good for what it's good for and it's handling
  my overly huge gmail without any trouble.* Oh and it's freeware
  and lots of reputable recommendations.* Similar tools exist for
  linux and I was jealous but then I found this.
  http://www.broobles.com/imapsize/index.php

References

  Visible links
  1. https://plus.google.com/s/%23Gmail