Sendmail+Cyrus IMAP "Data format error" and bounces

[Sergey]

On Tuesday 17 March 2020, Andrea Venturoli wrote:

> From time to time, I receive some message that are refused
> and bounce. Do to possible blacklisting, I *really* want to
> avoid bounces. 
 
I use Sendmail+Cyrus a very long time and I not remember this
problem exactly. Cyrus is not receive messages in two cases:
1) message contains 8-bit symbols (not encoded to base64 or
   QP) in header;
2) message contains NUL character.

The first is subject of reject8bit option in imapd.conf. About second look
to https://groups.google.com/forum/#!topic/comp.mail.sendmail/xW7S5vXDNtY

May be the first one causes the "Data format error" message.

-- 
Regards, Sergey