The experienced 'Relay Access Denied' message is pretty much similar than in Postfix without a Proxy.
So, I went back to the configuration which I think is correct:

smtp_auth none;
xclient on;

The only issue with this configuration is, that Outlook cannot authenticate - which is the same for IOS by the way as I found out...

After a while, I had a wild idea! What, if I just add the keywords 'AUTH PLAIN LOGIN' to the smtp_capabilities?
This is presented after EHLO in normal postfix
And surprise, this worked!

Hence my config is now:

xclient on;
smtp_auth none;
smtp_capabilities "SIZE 10485760" ENHANCEDSTATUSCODES 8BITMIME DSN "AUTH PLAIN LOGIN";

Does anybody see an issue with this?

Which sparcs another question: Postfix also offers: PIPELINING, VRFY, ETRN, AUTH=PLAIN LOGIN.

Can these keywords be added to the smtp_capabilities because Nginx is not changing the capabilities?

Thanks,
Cugar15



This seems to indicate that an email Client is able to authenticate....