Slow Mail app Wheel keeps turning every time I touch the program

Question

My mail app has recently become cumbersome. Every time I write a few lines the little wheel turns until it seems it has saved to disc or to the iDisk. It is becoming a real pain in the neck. I noticed that it is also happening with Pages app too. I have archived 95% of all the old emails.
The genius in the local Mac Store said it is because it is syncing with MobileMe all the time. So I switched the syncing to Manual. but this has not solved the problem. Does anyone else have the same problem or have any ideas how to cure it. I have tried al the normal things like repair permissions, rebuild mailboxes etc.

Answer 1

I have just tried to change the new settings in Mail preferences.
The IMAP account setting have a tick box for IDLE (it is at the bottom of the "advanced" panel on the recent upgraded Mail 3). This is a setting which makes the IMAP accounts look up all the time to get the "push" email. I have set them to "off" and it seems to make a difference, but I am not sure that this is the cause.
However, It would seem realistic that if you have slow broadband speeds it will have a bigger effect than if you have fast broadband speeds. Here we have about 2 MBpS download and 0.3MBpS uploading.