@j12t@j12t.social we're also in the market (of sorts) for a recommendation for email sending.
We've traditionally recommended Sendgrid to people because they had a (very) generous free tier, but that has since gone the way of the dodo.
Right now we recommend Mailgun but I am not sure of the specifics, we selected it simply because there exists a free tier.
We currently use SendGrid for our transactional emails.
The crappy part is that acting as a free MTA means people abuse your generosity. That's why these services aren't free. Sucks that bad actors ruin good things.