Mar 22 06:36:21 host postfix/cleanup: D6D441CA09A0: discard: header x-microsoft-antispam-message-info:? 5rSUbtg9a+8v7qvflcvdu8ODNNDgy6QCo+...etc...
According to Postfix header_checks documentation:
DISCARD optional text...
Claim successful delivery and silently discard the message. Do
not inspect the remainder of the input message. Log the
optional text if specified, otherwise log a generic message.
Someone configured Postfix to discard this message.
> Where can that be configured?
> I posted Header and Body checks.
> It is strange because the sender is a regular user the recipient
> emails from.
My guess is that your 'header_checks' regex /.icu/ is matching something
in the full x-microsoft-antispam-message-info header. Postfix does not
log all of very long headers and that's a very loose regex because you
have the wildcard '.' and probably meant /\.icu/ That seems like a very
risky pattern to me but do as you want with your own mail. More
generally, header_checks is a very weak tool for spam filtering by
design. If you want anything like spam control, you need something
Note that "x-microsoft-antispam-message-info" is not documented, but it
almost always contains >300 or <100 characters and most often is 428