Custom Email Not Working But Regular Email Does?

I tried searching for this but I couldn’t find a straight forward answer.

In the settings menu you have to enter an email for admin purposes, such as notifications for new users, new comments…etc.

When I put my personal email such as “example@gmail.com”, it works fine and I get my notifications.

But when I enter my domain email, such as “oliur@theultralinx.com” I don’t get any notifications.

My custom domain email is intergrated with Google Apps so I can use it like Gmail and with other Google services.

My site – UltraLinx

Anyone know how to solve this?