Help Email notification problem


I have a problem on my Huawei Ascend P7, as well as on my older Huawei Ascend Y330: Notifications of incoming emails (a hotmail account, defined as Exchange) sometimes function, sometimes not.
In other words: unreliable.

I am using the built in email function.

(The email icon on the home screen gets updated with a number in red, indicating number of unread emails. But there is usually no sound, no led signal, no email icon in the status field; no notification)

Judging from the number of complaints I have come across when surfing the ned on this issue, it is not related to any specific brand or model of phone, or even Andriod release.

Any suggestions, please ?
(Pardon my english, aswell as my illiteracy in smartphone usage; I am a newbie)