[exim] Frozen Bounce messages to unknown users

Hi list,

Recently I've been getting a lot of bounce messages sitting in my queue
that are intended for users that do not exist. These cannot be bounced
because they do not have a sender address, and they sit frozen in the
queue for 2 days before they are discarded. I have about 15000 of these
messages at any one time.

I am worried that exim is trying to deliver them every 30 minutes. This
shouldn't happen if the message is frozen correct?

Are there any dangers of changing ignore_bounce_errors_after to
something like 12h and dropping timeout_frozen_after to 2d from 7d?

TIA,

-John