Not receiving emails to Roundcube

Hi-

I have set up a new email amy@ndkhomes.com and it is not receiving emails to the inbox. I was able to send a test email out to my Gmail account, but nothing is received when sent to my amy@ndkhomes.com email. I then went and test the other emails we have for our company and they are also not recieving emails any more, I'm not sure how long it's been going on, but we need to get fixed ASAP and I don't know where to start. 

Thank you