By breaking I mean that just installing ONE app from here TMO or just installing ONE app from devel & testing or just making one mistake in x term you might end up with device that you need to reflash. Price what you got to pay for freedom provided. You are 100% responsible for actions you make to your device.

And I just said that this is multimedia device. If Nokias outdated business model where every piece of device is fragmented and targeted to specifically to particular market group comes as surprise then you should maybe learn more about Nokia. E is for business PERIOD DO NOT TRY TO USE N SERIES IN BUSINESS ENVIORNMENT. Capiche? Or Of course you can try but well...have fun tweaking

.edit
Let´s try to answer OP.

Hmm from advertisement page
"Nokia Messaging supports push email from your favourite services including Microsoft Live Hotmail, Yahoo! Mail, and Google Mail."

So first i would set up Nokia Messaging because it looks like it´s the way to go. About attachments. To me attachments do not get downloaded automatically. Maybe something to do with fact that I have installed modified Modest:

I also would try to experiment device and try updated modest:
http://talk.maemo.org/showthread.php?t=63291
"Normal warnings apply. Please backup before doing any experiments with your device"

..edit
Do not use POP3 if you do not want to download attachments
http://talk.maemo.org/showpost.php?p=508367&postcount=8