Disable MX lookups on Postfix?
I'm currently having an issue where mail is being rejected by my mail relay server; if I'm interpreting the issue correctly this is because Postfix insists on checking then does not recognise the sender's domain. Error message received:
5.7.1 SMTP; 550 5.7.1 sender domain does not exist> #SMTP#
What I would like is for Postfix not to check the domain; I have read around on the topic and have found ways to disable MX lookups by inserting square brackets around the destination address for relay settings within /etc/postfix/transport and /etc/postfix/master.cf; however, in this setup the server acts as a mail server to the internet and relaying is not configured using the relay statements within those files. I was wondering, does anyone know of another way to stop Postfix querying the domain, or indeed some other solution that might work in this instance?