Quickest way to download my Mobileme email account

The extra storage you have as a result of having been a MobileMe subscriber will be removed on 30 September unless you decide to pay to keep it ($40 p.a.).

If you decide not to keep it you can download some or all of your messages to your Mac, removing them from the iCloud server.

Create a new Mailbox in Mail on your Mac, making sure that it is listed under 'On My Mac'. Go to your iCloud mailbox, click on the top message of the ones you decide to download and the shift click on the bottom message to select them all. Drag them to the mailbox you just created. It will take some time to download them. If you have a lot of messages I shouldn't try to do them all at once or you may hang the process - I should do 100 or so at a time.

If you wish to pay to continue your current storage level, the instructions are here:

http://support.apple.com/kb/HT5527

Scroll down to 'How do I purchase my current plan?' and expand the section applicable to your computer or device.

All you emails are kept in (user)/Library/Mail but you should never tamper with that - deal with everything in the Mail application. You will find your downloaded emails in the mailbox you've downloaded them to. You can archive the mailbox if you wish (select it and click the cogwheel icon at the bottom) but it has to be in Mail for you to actually access them.

A quick test on one mailbox showed that it reduced the size to about 0.6 of what it was before. You would still need to delete the original mailbox from Mail once archived, and you would have to reimport the archived mailbox if you wanted to access the contents.

The simplest way to do that is to create a password protected disk image and put your archive(s) in that, though it will tend to take more space. The principle value of archiving is if you have years and years of back emails you can prevent them from cluttering up Mail.

Not really. However you should be careful about the number of messages in any one mailbox. I wouldn't go over a thousand or so - it can cause problems (though I'm not exactly sure at what point this is likely to start) - it's better to split them into different mailboxes. This is where it starts to be advantageous to archive them if you don't want a lot of mailboxes in the list in Mail. The number or mailboxes isn't a problem, it's how many messages are in them. Splitting them up by year would seem one good method.

Yes, dragging the messages removed them from the source folder. (If you want to copy rather than move, hold the option key down while dragging, but I assume you don't.)

The count is often a bit haywire. Give it a bit and see whether the actual usage has come down by a reasonable amount.

I did say to be a bit careful about how many you dragged in one go. You may be running the risk of hanging the entire system.