@Okenyon @BassMan Let me know if you/sparkpost makes any progress with bounce forwarding.
It's also important to have spam complaint forwarding (which Sendgrid offers)
@AmieDurr @Nuno
Nuno is right - Inbound Relay Webhooks don't work the same as far as I can see (admittedly, I haven't actually tried them). With Sendgrid you can just plug in a Bounce or Spam complaint forwarding address and then all bounce/spam complaint messages are forwarded to this email...