Good morning,

I can't seem to get the outbound relay service to work. When I send an email through it, I get a bounce back from the dynu server stating:

"The mail system <finen003@gmail.com>: host relay.dynu.com[168.235.105.136] said: 530 SMTP authentication is required. (in reply to RCPT TO command}"

So this makes me think I am not authenticated through dynu?

I do have /etc/postfix/sasl_password as:
[relay.dynu.com]:2525 relay@relay.finendale.com:Password

and I have main.cf containing:
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash: /etc/postfix/sasl_password
smtp_sasl_security_options = noanonymous

relayost = [relay.dynu.com]:2525
smtp_generic_maps = hash:/etc/postfix/generic

Am I missing something? Do I have the right ports called out? I am starting to get pretty frustrated in trying to set up this service so look forward to any help.

Four years later. Did you get the answer? I'm having the same experience on Ubuntu 21/xx.