[exim] Not freezing "unknown user"?

Is there anyway to not freeze a message that is a result of "user
unknown" from the back end? Using 4.24 currently.

Feb 8 14:07:14 nvoweb exim: 2005-02-08 14:07:14 1CyV5F-0002fb-JL <= <>
H=icho.ipe.tsukuba.ac.jp [130.158.65.1] P=smtp S=2235
Feb 8 14:07:14 nvoweb exim: 2005-02-08 14:07:14 1CyV5F-0002fb-JL **
mcdowell_72@??? <mcDowell_72@???> R=relay_router_nwl T=local_smtp:
SMTP error from remote mailer after RCPT TO:<mcDowell_72@???>: host
192.168.221.211 [192.168.221.211]: 550 5.1.1 User unknown
Feb 8 14:07:14 nvoweb exim: 2005-02-08 14:07:14 1CyV5F-0002fb-JL Frozen
(delivery error message)
Feb 8 14:07:18 nvoweb exim: 2005-02-08 14:07:18 1CyV5G-0002fv-4n **
ellis@??? <Ellis@???> R=lookuphost T=remote_smtp: SMTP
error from remote mailer after RCPT TO:<Ellis@???>: host
smtp.ctimail.com [203.186.94.58]: 550 5.1.1 <Ellis@???>... USER
unknown