hope you can assist me in this case.
I am administrating an Postfix server which is used for newsletters. Recently one of the major recipient domains changed their policies to only accept one email per smtp session/connection. To adhere to their policy I found the following settings in main.cf to be kind of useful as they refer to concurrency of email delivery, though it doesn't seem to help.
(I've tested with values as low as 1)
The error I am facing is: dsn=4.4.2, status=deferred, along with a link telling me to send a single email per SMTP connection.
Postfix version: 2.9.6
Any suggestions will be appreciated!