Setting up Postfix on an OVH box seems to still work, though you do have to watch deliverability to Outlook, Google & Yahoo.
The latter two will send emails to spam, but Outlook.com hosted addresses are especially insidious as they'll accept emails, but throw them straight to /dev/null (or the Windows equivalent) with no trace in the user's inbox or spam.
@bikecurious @twylo Mailserver (and this server) are in my basement, racked up on a UPS, on Small Business class FttH. Technically a 'residental' ISP, though. Outbound relaying goes through them, but inbound delivery comes straight to me on standard ports.
I'm able to e-mail and keep in touch with friends and family on Gmail, other-ISP mail, etc. just fine.
I... don't know anyone with an Outlook.com address, though, so maybe that's it.
Deliverability issues have generally resolved themselves whenever I've spent a bit of time getting multiple users to pull us out of spam with the respective provider, we don't use a mail relay tho.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko