[Assp-test] expired MSGID??

[Katip <ka...@ka...>]

v.1.4.1.3.00

I saw this for the first time ever:

Oct-6-08 09:16:10 id-73770-00701 x12.58.x5.1x <> to: us...@ou... 
  Bayesian Check - Prob: 0.00000 => ham
Oct-6-08 09:16:10 id-73770-00701 [MessageOK] x12.58.x5.1x <> to: 
us...@ou... message ok [Read 26 09 2008]
Oct-6-08 09:16:10 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]
Oct-6-08 09:16:10 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]
Oct-6-08 09:16:10 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]
Oct-6-08 09:16:10 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]

(... thousands of same lines within 8-9 minutes)

Oct-6-08 09:24:55 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]
Oct-6-08 09:24:55 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]
Oct-6-08 09:24:55 id-73770-00701 [MSGID-sig] x12.58.x5.1x <> to: 
us...@ou... info: found expired MSGID signature in [In-Reply-To:]
Oct-6-08 09:25:00 Starting as a service (Server was totally blocked. 
perl.exe killed and service restarted manually)

What is an "expired MSGID"?? TIA

KAtip