Mail not being received or sent [solved]

New box set up last week … noticed an issue in the mail queue with a mail not being sent which let to looking at logs … and finding several entries for incoming mail that is being rejected.

The entries are similar to:

Jan 31 23:44:45 dallas postfix/smtpd[10351]: NOQUEUE: reject: RCPT from unknown[]: 450 4.1.8 <Public.Business@SOS.STATE.CO.US>: Sender address rejected: Domain not found; from=<Public.Business@SOS.STATE.CO.US> to…

(that is not the entire line in the log entry)

What it appears to me is that MiaB is not doing lookups properly. How do I troubleshoot this?

After testing it seems that the ISP’s DNS was being very flaky. The owner of the box made an unsupported modification and changed the resolver to a major DNS provider.

Perhaps this is something that should be added to the MiaB install scripts?

Pi-Hole allows setting out different DNS providers (Like OpenDNS, Google,, Norton, etc,etc). Though that project is for something completely different, having the ability to change DNS I think would be a neat feature, but how to implement it is a different story.