My Samsung Galaxy Tab 2 has this problem even with my yahoo account. Generally a restart, will fix it. If the problem is more persistent, hard reset your device. Make sure to back all your data up. I have to do this to my brothers phone too. Its an android issue, that comes out of no where and then goes away sometimes.
Setting it for 15 minutes will also drain your battery life and use more data, both your wireless data and hughesnet data.