If you run your own mail server and set up everything correctly, including SPF, DKIM, and DMARC, most major providers will still either silently drop your messages or always mark them as spam, unless you pay money for a relay (e.g.: postmarkapp.com).
I have had my domain for 20 years and IP for years, and set up everything correctly, and Microsoft and Google rarely accepted my messages.
mailfence.com ?