Thank you.  What do you think is the solution?  This log is not enabled so there is no audit trail.   Tell me again where is the switch to enable this log.   I think this one kept increasing to an enormous size so I disabled it. 

Is there an obvious solution?

I asked which log?  How do I set the switches for various logs?  There is a plethora of logs.  The question is very simple.  Mail from me to my spouse is bouncing.  It is not spam.  We know each other.   We are both on the same server.  How can this be tagged as spam???

Here is the message this morning.  All emails are 100% fully authenticated with DMARC, SPF and DKIM:

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed.   

  patty@xxxx.com
    host mail.myhost.com [13.xx.xx.xxx]
    SMTP error from remote mail server after RCPT TO:<patty@xxx.com>:
    554 5.7.1 <patty@xxx.com>: Recipient address rejected:
    SMTP AUTH is required, or it is a spam with forged sender domain

Where can I manually enter whitelisted or blacklisted email accounts?

thank you.   In general iRedMail is working fabulously except for tiny errors

Thank you.   I do not understand this:  send email SMTP AUTH  in MUA.     Too cryptic.

It's only this one address that bounces.  We are both on the same email server.  How could it possibly bounce.  The source is the same.