I found Orange email to be problematic in the past, so I don't use it.
I have a Gmail account that set itself up automatically on my Desire, plus 6 personal POP email accounts that I set up in just a few mins using the email providers POP settings.
Not sure if any of the accounts are push, but I've set the poll interval on each account depending on their importance and it works very well. The data usage is minimal because I only download headers until I know the message is important enough to download.