Mobile email – caught between the push and the pull

I am getting very excited with the up and coming expiration of my existing cell phone contract.  I will be getting an iPhone.  My wife will have hers before me since she will qualify for the discounted price of the phone sooner but I anticipate that in the not too distant future I will also share in the experience.  I currently have an HTC phone running Windows Mobile 5.0.  I have had various mixed experiences with managing my email through this phone and it has dawned on me that there is a missing service:  a unified email portal that aggregates multiple addresses into a single account interface.  A friend pointed out to me Web2Mail and while they do have an aggregation email scheme,  you require getting a whole new email address.  Also, when you respond to an email address, your reply does not carry the original address from the email.  For example, a friend emails you at first.last@gmail.com and then you get it on your phone after signing up with Web2Mail by them actively syncing to your remote device.  When you respond to the message, it will show as being sent from your first.last@web2mail.com address.  Bummer.  There has to be a way through proper account security to alias this functionality to a central account.  It is the essence of SMTP as a protocol.  I need to explore why this doesn’t exist as a service:  Email account aggregation with a robust synchronizing push-based capability.