Yeah I'm seeing this too! Identical in fact. This is what I did to
fix this: I added this to my /etc/mail/access file for my local
server that sends this messages to me:
SRV_Features:127.0.0.1 L U G
Specifically, I added the U and G features, (I already had the L
feature disabled for localhost). Uppercase letter disables the
feature, lowercase enables it.
I found the U and G mentioned here:
https://forums.oracle.com/ords/apexds/post/solaris-11-4-sendmail-issue-after-sendmail-8-18-1-update-7312
I did not try this suggestion to use U2 and G2 that he mentioned. If
you do let me know.