I have a problem receiving email messages. I can send them, but I cannot receive them. 

I added the MX entries and everything looks fine but when I try to send an email from my gmail account, I get this message:

Delivery to the following recipient failed permanently:

      info@zadarhalf.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain  zadarhalf.com  by  zadarhalf.com . [138.201.132.205].

The error that the other server returned was:
550-Please turn on SMTP Authentication in your mail client.
550-mail-lf0-f51.google.com  [209.85.215.51]:33895 is not permitted to relay
550 through this server without authentication.

Thank you in advance for your help!