Ciro Santilli The first one Ciro Santilli managed to get working in 2022, and which has a free plan.
You can either verify your sending domain by adding 3 DNS records.
Saw the email on Gmail, but Microsoft Outlook did put it into junk though. Yahoo mail also worked fine.
100 emails a day is not insane, but it is forever and appropriate for a test, I'm happy with that.