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Best free/cheap web host for DIY email
(aussie.zone)
A place to share alternatives to popular online services that can be self-hosted without giving up privacy or locking you into a service you don't control.
Tunnel broker blocks port 25 by default, but you can ask nicely and they’ll open it for you. It’s a good option if you don’t have an IPv6 address otherwise.
Having an IPv6 only mail server is potentially risky, though… some other mail servers may only talk IPv4.