Samsung Zeal / Alias 2 SCH-U750

I have the Mobile Email application, and I have my Yahoo! and Hotmail email addresses registered on there. I have set it up to notify me on my phone when I have new email in either account, but it has only notified me occasionally, and not every time when I have new email. Could someone please guide me through the setup of this feature for Mobile Email so that my phone will notify me when I have new email in either of my accounts? I would deeply appreciate it. Thanks.