To those who cannot send messages using GMail account tied to Nokia Messaging account:
checks SMTP server on your Nokia Messaing account. After logging to to email.nokia.com, click on "Edit settings". Then click on button "Email server settings".
It should be: smtp.gmail.com, port 465.

In my case, smtp related fields were not filled in. Result: emails were sent from Nokia servers but with header set to my GMail address. Side effects: no mails in GMail sent folder, using reply to option was breaking threads.