Hi @PJV
There are reports on this and several users have come out with some workarounds which have pretty much sorted this, some of them are listed below try out these and check if they are helpful.
Check if it is possible to use another email account (which supports TLS 1.0) instead of Office 365 to send the health report.
The workaround would also be to specify the MX for your domain at Office 365 as the SMTP server, port 25 with no auth or SSL/TLS. Since it's only emailing you, it's not relaying and it will be delivering the health report.
Here is a thread as well that discusses the same issue and you can try out some steps from this and see if that helps you to sort the Issue.
Hope this resolves your Query!!
--
--If the reply is helpful, please Upvote and Accept it as an answer–