Dovecot not sending emails externally when domain is hosted on cyberpanel

Hi All,

Whenever I go to send a email using the php mail(); function or using the sendmail application on my server I am only able to send emails to domains which are not hosted on Cyber Panel.

i.e.

If I have a website with the domain name example.com

I am unable to email [email protected] I get:
Jan 15 13:15:24 ip-REDACTED_IP postfix/pickup[677629]: BB3691C3AC54: uid=5003 from=<REDACTED_ACCOUNT>
Jan 15 13:15:24 ip-REDACTED_IP postfix/cleanup[677634]: BB3691C3AC54: message-id=20210115131524.BB3691C3AC54@localhost
Jan 15 13:15:24 ip-REDACTED_IP postfix/qmgr[677630]: BB3691C3AC54: from=**REDACTED_ACCOUNT**@localhost, size=316, nrcpt=1 (queue active)
Jan 15 13:15:24 ip-REDACTED_IP postfix/pipe[677638]: BB3691C3AC54: to=[email protected], relay=dovecot, delay=0.07, delays=0.05/0/0/0.02, dsn=5.1.1, status=bounced (user unknown)
Jan 15 13:15:24 ip-REDACTED_IP postfix/cleanup[677634]: CB7841C3AC55: message-id=20210115131524.CB7841C3AC55@localhost
Jan 15 13:15:24 ip-REDACTED_IP postfix/qmgr[677630]: CB7841C3AC55: from=<>, size=2150, nrcpt=1 (queue active)
Jan 15 13:15:24 ip-REDACTED_IP postfix/bounce[677642]: BB3691C3AC54: sender non-delivery notification: CB7841C3AC55
Jan 15 13:15:24 ip-REDACTED_IP postfix/qmgr[677630]: BB3691C3AC54: removed
Jan 15 13:15:24 ip-REDACTED_IP postfix/local[677643]: CB7841C3AC55: to=**REDACTED_ACCOUNT**@localhost, relay=local, delay=0.01, delays=0/0/0/0, dsn=2.0.0, status=sent (delivered to mailbox)
Jan 15 13:15:24 ip-REDACTED_IP postfix/qmgr[677630]: CB7841C3AC55: removed

The server where I want dovecot to deliver the mail is not hosted on the same machine and is instead hosted with a cloud email provider.

My Goal is to be able to send emails to email addresses which end in domains that I am hosting but have it deliver the email to a remote server.

I have tested sending an email to a generic Gmail address and the email is delivered without issue. It is only when CyberPanel also hosts the domain name.

The Server is hosted on AWS. The server has been granted permission by AWS to send emails on port 25. This is confirmed by the successful email delivery to a gmail address.