Email aliases are failing - Club 3362

Email forwarding has historically worked, but at the moment emails to committee members are failing to be forwarded. This happens for multiple club committee member accounts (tested with president@melbournetoastmasters.com and officers@melbournetoastmasters.com)
Please advise what is required to resolve this; the returned email message is below.

Delivery to the following recipient failed permanently:

officers@melbournetoastmasters.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain melbournetoastmasters.com by mail.melbournetoastmasters.com. [50.19.253.65].

The error that the other server returned was:
550 5.7.1 <officers@melbournetoastmasters.com>... Relaying denied. Proper authentication required.

Thank you, Alan

Alan,

I believe this is a custom domain issue, so I need to defer to Brian or Steve for their expertise.

Your domain name does not seem to be set up correctly

1) your email MX records you need to remove these 2 lines

melbournetoastmasters.com. 3599 IN MX 20 mx2.netregistry.net.
melbournetoastmasters.com. 3599 IN MX 10 mx3.netregistry.net.

2) there is no A record for the base domain melbournetoastmasters.com add the following

melbournetoastmasters.com. 3599 IN A 50.19.253.65