Hello @DanielCollins Happy you are here
Unfortunately you have not given any diagnostic errors to go by but i have seen the host mail.ecmindustrial.com.au The records are ok
Check your mail transport agent (postfix) . Post the contents of https://<IP Address>:8090/serverlogs/emaillogs or nano /var/log/maillog
If you are using GCP they discourage email sending See how to fix this Setup External SMTP on Google Cloud Platform (GCP)