Oh my... I'm so stupid - I missed this as well and set up two email accounts manually and have been using it that way for the last 6 months! Not bad, but I'll give the push email a whirl :-/
I have an N900 with vodafone UK & I re-flashed my phone last week as it was starting to struggle with some corrupted libraries after playing around with extras-devel packages.
So I grabbed the latest firmware and vanilla files and all sorted without a hitch.
However, now I try to set up Nokia Messaging again, every time it just tells me "Unable to contact e-mail provider. Please check your settings".
I know the email address is the one that I used to set up Nokia Messaging at http://email.nokia.com. I can log in fine there. Have I missed something that I need to configure somewhere?
I am having the same problems, before I reflashed I used to have a mail account called "nokia messaging" when click on that I would then have a choice of my hotmail account or my imap account for work. However now when I go to Service Provider "Nokia Messaging" it just adds my hotmail account as a standard account rather a Nokia Messaging account. This is beginning to REALLY annoy me.