I can send emails but when i send a repaly for that mail it is not delivering

I can send emails but when i send a repaly for that mail it is not delivering

Delivery to the following recipient failed permanently:

      sales@bringkeralaonline.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain bringkeralaonline.com by bringkeralaonline.com. [172.96.11.112].

The error that the other server returned was:
550-Please turn on SMTP Authentication in your mail client.
550-mail-ua0-f181.google.com [209.85.217.181]:33172 is not permitted to relay
550 through this server without authentication.

Showing Like that . But MX RECORDS ARE Clear http://mxtoolbox.com/domain/bringkeralaonline.com/

And also how to setep spf records ?