Fix Qmail smtp error 5.7.1 on one domain on a root server. The server is running FC4. Only one domain's email doesn't work... others are OK. Mail sent to that domain gets the error message:
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
[url removed, login to view] #5.5.0 smtp
553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
Mailman is also on the server but I had a programmer install qmail instead. The server uses a Plesk 7.5 control panel. I can chat and assist with access to the server.