newscloud wrote:
Sender address rejected: User unknown in virtual mailbox table; from=<bounce+f3ca76.809f-jeff=inbound.hong2.com@hong2.com> to=<jeff@inbound.hong2.com>
This log makes sense.
If the Sender address is a domain hosted on your server, Postfix requires this client to perform SMTP AUTH first, after auth succeed, Postfix accepts email and sends it out. This is default setting in iRedMail, which prevents your server to be an open relay.
Both hong2.com and 'inbound.hong2.com' are hosted on your server, so Postfix will ask it to perform SMTP AUTH, but obviously, it won't do this.