Originally Posted by concept21
Is it imperative to use sasl auth in order that the relaying server will talk with the upstream partner?
So if I get it right, you just want to send outgoing mails via any provider you have? Then you have to configure the relay you want to use.
For sure it is imperative, everything else would be an open door for spammers as it would be an so called open relay.
Or what do you mean by "I also put its ip in the upstream partner's config:" do you configure the "upstream partner" as well and it's a server controlled by you?!
Anyhow if your task is just to configure the postfix of your ubuntu machine to send mails via the mailserver of any of your providers (which typically requires an authentication) have a look here: http://www.howtoforge.com/how-to-rel...postfix-server