Self-Hosted Mail servers have the problem that most ISP's will automatically add all of their Service IP;s to BlackLists specifically to prevent people from running mail services on their Internet connections.

Unless you have a Commercial Line that has be specifically designated for hosting content then it is likely any IP you are issued is added to Google/Microsoft/etc Blacklist by the ISP. Most of them clearly spell out in their terms that running a Mail Server on the circuit is forbidden.