I have an IronPort box that's been trying to bounce the same mail to my mail server, on the hour for nearly three days.
The sender address is being rejected for obvious reasons:
NOQUEUE: reject: RCPT from ironport2-out.teksavvy.com[18.104.22.168]: 450 4.1.8 <email@example.com
>: Sender address rejected: Domain not found; from=<firstname.lastname@example.org
I tried to whitelist the server, blacklist it and a bunch of other things but the reject_unknown_sender_domain still kicks in and, becasue it's only a 450 response, they try again an hour later.
I thought I'd try "soft_bounce=no" but the GUI won't allow me to set that.
I can get soft_bounce=yes by setting soft bounce to "enabled" in the GUI but selecting either "Only in PostScreen" or "Disabled" just clears soft_bounce from main.cf.
I thought Disabled should set soft_bounce=no but wanted to ask what you think?