Postfix SMTP server: Emails not being queued for retry when greylisted [submission by email clients]

I have recently configured my own postfix server, however there is one thing left that's stumping me.

When sending emails via thunderbird to a server with greylisting enabled, I am instantly receiving a message stating that it is unable to send, rather than be put into a queue and attempt to send later.

I assume this would also have ramifications if I try to send to an email server that's having issues.

1 Answer

1. Enable submission port (port 587) in master.cf
   
2. Double check that submission port accepts emails only after successful SMTP AUTH
3. Turn off greylisting for messages received via submission port
4. Make your email clients send messages via submission port