Yep... I have been the target of multiple spam attacks involving 1000s of messages and even DoS attacks with DMs. But none of that made a dent in my DM experience on Amethyst.

All attacks can be resolved from a client. None of them will ever be fully resolved by the relay.

You can even keep a client running that simply performs any WOT assessment after decrypting the DMs. But it is the client's role.