Looping messages when postmaster@domain does not exist

For some reason when people email my RT system, and for whatever reason
the delivery fails (I think its when the sender has a badaddress), and
RT sends out a:

RT could not load a valid user, and RT’s configuration does not allow

for the creation of a new user for this email (postmaster@domain.com)

You might need to grant ‘Everyone’ the right ‘CreateTicket’ for the

queue general.

This message is bounced back to their domain, which replies the same.

Short of making people enable postmaster@domain accounts, how can I stop
RT from looping on these emails?