I am having issues with this too. I contacted Elementor support who suggested a Yahoo or Gmail address was more reliable!
Not sure where that advice comes from, but the address that they won’t accept is an Office 365 address on a business domain. SPF/DKIM/DMARC are all set up, and works just fine for everyone else.
Elementor support appear to have given up with me, so not currently inclined to invest in their product, which is a shame as it does appear useful, and I potentially have a number of follow up sites to migrate in a similar way.
