@matthieu @feld yes, many chatmail servers are not ddos protected likely. Some run in environments where ddos protection exists.
Fwiw ddossing all email servers world wide is probably a daunting task and would bring most governments and institutions to a grinding halt.
We have stopped publishing about new chatmail server setups half a year ago btw and are to devise a decentralized way to distribute information about chatmail servers. We don't want to provide public block lists, basically.