Delivery to the following recipient failed permanently:

  @investergy.co.uk

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain investergy.co.uk by mx.zohomail.com. [72.5.230.114].

The error that the other server returned was:
554 5.2.3 MailPolicy violation Error delivering to mailboxes

This has happened 4 times this afternoon when trying to forward an email together with attachment from my Gmail account.   Advice please would be much appreciated