I am having issues receiving e-mail from external sources.

I've just migrated my e-mails to Zoho from HostGator.

Under MX Records, I have the following:

mx.zoho.com

Priority: 10

mx2.zoho.com

Priority: 20

I have e-mail my e-mail hello@collectify.com.au using gmail and also my other work e-mail address. They both result in the following error messages:

______________________________________________

Delivery to the following recipient failed permanently:

      hello@collectify.com.au

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain  collectify.com.au  by  mail.collectify.com.au . [192.185.22.184].

The error that the other server returned was:
550-Please turn on SMTP Authentication in your mail client, or login to the
550-IMAP/POP3 server before sending your message.   mail-oi0-f46.google.com
550-[209.85.218.46]:36388 is not permitted to relay through this server without
550 

Can someone please assist? As I really need to finalise the setup of my Discourse forum.

Thanks.