email is a standard protocol. You can run your own server using FOSS software in 5 minutes if you start now. One of the biggest problems is that you will have a hard time “federating” to gmail and others due to the spam problematic, but that is something that we will see with Lemmy, too. Currently I can spin up my own server and start pushing shit to lemmy.world and other bigger instances, but I feel that this will change with the coming spam waves