When I found mobipush.com this is quite a good candidate to solve my problem, as they offers retrieving emails from all imap/pop email accounts and push it to your windows mobile device using Microsoft Direct Push technology. Here’s the features offered:

Features & Benefits

• Push eMail for IMAP and POP3 (Including Gmail, Yahoo!, AOL, Exchange…)
• Compatible with all DirectPush devices, including Windows Mobile SmartPhone and PocketPC
• No software or Hardware installation required
• Use your existing eMail account
• Synchronize Read/Unread Status and eMail deletions
• Secure communication using SSL encryption
• Synchronize up to 5 personal and/or business eMail Accounts
• Remote device wipe in case your device is lost or stolen

The good thing is, when you replied an email, the email will appears from original to: email address from sender, not from the default email account, which is not offered by mail2web.com. The only negative I found is only lack of syncing contacts, appointments, calendar events etc compared to syncing with real exchange server. But hey, currently I only need it to sync emails.

If you configure the push mail to access IMAP email accounts supporting IMAP idle commands, your email(s) will almost instantly delivered to your mobile device. But if it does not suport IMAP idle or only support POP access, is not as instant as it’s a pull email. Usually it checks for new emails every 5 to 10 minutes for POP emails.