WordPress not sending e-mails

Hi! I’m working great with wordpress but recently i discovered something, my blog is not sendig e-mails.

I don’t know what’s exactly happening but please tell me if there is a plugin i can use to fix it or how can i fix it.

I think the email sending is called by a php function but i don’t know what function exactly so please! tell me how is it named to ask my free hosting provider if its active.

Thanks a lot