Emails not being received through Gsuite and Shopify

Hi there,

Since setting up our email account for Gsuite a lot of customers have had their emails bounce, but some customers emails come through fine.

Also when a customer fills out and sends through a contact form they don't arrive, even though our email we receive notifications from shopify is accurate. Here is the contact us page: https://cskgifts.com/pages/contact-us

I'd appreciate it if you could get in touch with me and perhaps suggest a reason behind why this is happening so I know you've taken the time to read this and understand the issue.

Thanks

Cameron