Are you trying to fetch mail through a 3G connection, or a wireless internet connection? I experienced that I was unable to fetch mail on the mail account through a 3G connection, and this was because my phone internet connection was set to WAP and not INTERNET. When using a WAP connection, there was a proxy server that closed the email ports - but when using INTERNET connection, all ports were open, and I could access imap mail normally. This might be a tip for others...