The “From” header would only be in a recipient’s email, and the addressed used there (often a bounce specific address) is the one that would be logged on my mail server.
Do you know the IP address of the machine sending the weekly issue? there is nothing on 2018/04/03 that seems to match. I have:
18:12:13 mail postfix/smtpd: 40FTzx3GZrzbRTr: permit: DATA from mail.tidbits.com[220.127.116.11]: action=permit for Data command=DATA ; from=<email@example.com> to=<firstname.lastname@example.org> proto=ESMTP helo=<mail.tidbits.com>
But that’s a TBT post, not the issue.
there is also
18:21:47 mail postfix/smtpd: 40FVBz5txCzbRTr: permit: DATA from o3.lv30n.shared.sendgrid.net[18.104.22.168]: action=permit for Data command=DATA ; from=<email@example.com> to=<firstname.lastname@example.org> proto=ESMTP helo=<o3.lv30n.shared.sendgrid.net>
but the time codes don’t match at all. I’ll check for that message ID and see if I can track down what happened to that message.Probably it was tagged as spam and my list account has a very low threshold for discarding spam.