Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
plus 1 for Benjamin's very helpful post on page 3 of this thread.
This fixes it.
A little convoluted if you are not an e-mail admin, but follow the steps he lays out & it works.
follow his link to https://www.alitajran.com/configure-dkim-record-for-office-365/
As a prior step, I added the the TXT records mentioned under https://www.gmail.com/postmaster/
This DID NOT fix the gmail bulk BCC issue, but I've left them in.
Thank you Benjamin !