[Exim] is "Message is frozen" an error or not ?

Hello,

Too many threads about this "message is frozen" thing...
Can someone tell me what can be the cause(s) of this (from mainlog) :

2001-04-24 06:15:41 145zyP-0008WA-00 Message is frozen
2001-04-24 06:15:41 145zyP-0008W3-00 Message is frozen
2001-04-24 06:15:41 145zyQ-0008WA-00 Message is frozen
2001-04-24 06:15:41 145zyQ-0008W3-00 Message is frozen
2001-04-24 06:15:41 145zyR-0008Vu-00 Message is frozen
2001-04-24 06:15:41 145zyR-0008W3-00 Message is frozen
2001-04-24 06:15:41 145zyR-0008W3-01 Message is frozen
2001-04-24 06:15:41 145zyS-0008Vu-00 Message is frozen
etc...
and sometimes it goes on and on for hundreds of lines...

Is this normal or not ? Should it be fixed or left as is ?

Thanks a lot in advance.

--------------------------------
Dr Felix Shumelinsky
Ortho. Surgery Dept. - ULB
Free University of Brussels
Phone: +32 (0)495 51.67.42