After installing Windows 10 on my Lumia 640 xl - new email alarm disabled. How can I re-enable it?

[Windows Central Question]

after installing windows 10 in my lumia 640 xl - new email alarm disable

i had used windows phone lumia 640 xl. Recently i updated it windows 10 through windows insider programme. Everything is perfectly running but as soon as i receive new email, it does not notify / flash / alarm me in locked screen.