Ah, gotcha. Feel like I've got the existing MX stuck in my mental model. Honestly with all of the existing DNS record based "authentication" with SPF, DKIM, DMA

Ah, gotcha. Feel like I've got the existing MX stuck in my mental model. Honestly with all of the existing DNS record based "authentication" with SPF, DKIM, DMARC its already a mess for bulk senders too lol. Thanks for putting these thoughts together :-)