Relay access denied using Usermin

I just realized that usermin denies access when trying to send mail outside its domain. I can send mail to another person on the same domain but I cannot send mail to gmail or hotmail for example.

Was this by design? I have tried changing some configuration in Servers - > Postfix -> SMTP Authentication And Encryption.

I can send emails no problems with a webmail like roundcube, it is just webmin that doesn’t work and I assumed it didn’t auth and maybe expected local relaying but having check marks for that in SMTP Authentication And Encryption did not seem to make a difference.

I have two copies of virtualmin running with webmin and they both provide this error.

Any ideas?

Have a look in your /etc/postfix/ file. What have you got for smtp_relay_restrictions and mynetworks?

in the file I ended up blocking this

smtpd_relay_restrictions = permit_sasl_authenticated reject_unauth_destination permit_inet_interfaces permit_mynetworks

restart postfix and now I can use webmin to send email from the domains I host.

I didn’t add this line nor did any modifications so I can only assume that this was created on a fresh install of CentOS7 or virtualmin install. I will spin up a VM to see for myself.