Hosted Exchange and/or something like mail2web is definitely the way to go for instant mail transfers but well...
1) Your battery life is going to suck if you go with push email and receive a LOT of emails.
2) And not to be rude, but... unless you're doing national security or are the executive assistant to God, you're really not so important that you shouldn't just use send/receive if you're expecting something or just realizing that a couple minutes delay isn't going to kill you. And in the moments where urgent communication is needed, there are more appropriate instant means like actually calling or texting or IM.
