npopw can live anywhere, does not require any installation (other than copy the npop.exe to the appropriate place), handles downloading just the message headers (configurable), multiple email accounts, attachments (receiving and sending).
The website where is use to be maintained has gone off-line, however I can a copy of the latest version (I think) V1.0.1.4 Beta 2, which is
here.
I've use it for the past 3 years, via ActiveSync, Wifi, and Mobile phone dialups without a problem.
And it is free.
If you map the "Messaging" button (button #3) to npop.exe and configure npop to "Check e-mail on start", it will poll for email each time you press the messaging button.
Negatives: does not support IMAP or SSL (i.e. gmail)
I've got a copy of the source code if someone fancies enhancing it - it is
here
Adrian