My Exchange 2016 seems to be unable to sends email to a compagny and I notice that it could be because of the header which is different then others:
Total retry attempts: 16
Server returned '400 4.4.7 Message delayed'
Here's the header in question:
[Contacting distmorissette.com [126.96.36.199]...]
220-rwh01.bigtek.org ESMTP Exim 4.91 #1 Thu, 14 Feb 2019 16:37:13 -0500
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.