New Users Not Reciving Validation Email

Recently, I noticed when a new user attempts to register for the site they do not receive a validation email. I’m not sure how long this is been going on, but I feel like awhile.

The odd part if I add a user manually and send the user an email with their password they receive that just fine. In addition, I’ve tested the server by doing a simple PHP email send on a page. That works fine as well.

If just appears to be the specific email related to new user validation.

Does anyone know where I might begin to look to fix this.

Thank you.