[Exim] question regarding freezing/thawing

I noticed an odd thing regarding a message being continually frozen and
thawed. I can't see an obvious cause, though I'm sure it's there. I have
a message to mailer-daemon@???, sitting on the server
mail.cinergycom.net. It's not a valid email domain, I suspect it got
there as a bounce message. Anyway, because of the situation, the message
freezes. A copy of msglog (there are more lines than this but they're
all the same:

2003-03-21 18:50:39 mailer-daemon@??? <Mailer-Daemon@???> R=lookuphost defer (-1): remote host address is the local host*** Frozen
2003-03-21 18:54:40 mailer-daemon@??? <Mailer-Daemon@???> R=lookuphost defer (-1): remote host address is the local host*** Frozen
2003-03-21 19:05:24 mailer-daemon@??? <Mailer-Daemon@???> R=lookuphost defer (-1): remote host address is the local host*** Frozen

looking in mainlog to see why it keeps getting thawed, I see this:
2003-03-21 19:07:46 18wWRl-0005VO-0s Unfrozen by errmsg timer. my config
has auto_thaw set for 12h.

this is 4.14. any ideas?

--John