Also using PurelyMail, tt’s the cheapest non-free email service I can find.
It passes email delivery tests, setup SPF, DKIM and DMARC easily without issue.
The downside is that it’s basically one man handling whole this service, but I assume this service has been fully automated because the margin of profit is so low.
I wish there is
everything
for Linux.fsearch has the looks but last time I tried I needs to wait for it to scan, no background indexing.