Loop prevention between two rt systems

Hello,

We just had an incident where our rt system and another groups rt system
got into a loop with auto-responding. I may be mistaken, but I thought
there were mechanisms in place to prevent this, as I’m pretty sure our
system has interacted with other rt systems in the past without any
problem. We’re running rt v1.0.4 with qmail as the mailer. Not sure what
they’re running on the other system. Any idea what might have caused
this? Thanks!