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.