error user registration

Hi, I have a problem.
with dashboard , I can create users perfectly .
But people can not register on my blog. I can see your registration dashboard , but do not receive the email with which generate a password.

I have enabled logging user , I tried to make it work with the plugin mail with gmail smtp because the fault is with that wordpress does not send the email .

I recivo mail when a new user is registered , but the problem is they do not , making it impossible to really register .
It is a very serious problem I need to solve, I’m desperate .
I’ve got to change hosting provider thinking that was the problem…

Thank you very much .