Hello all,

I would like to assist the owners of a mailing list I am subscribed
to in avoiding the following wrong error message:

Apparently since the list has moved to another server, a lot but
not all of the list members get the following error message each
time they send a mail to the list:

--------------------------

Subject: Rejected posting to [log in to unmask]

Your message  is being returned to  you unprocessed because it
appears to have already been distributed to the HYPNOS  list. That is,
a message with identical text (but  possibly with different  mail
headers) has  been posted to  the list recently, either by you or by
someone else. If you have a good reason to resend this message  to the
 list (for instance  because you have  been notified  of a hardware
failure with  loss of data), please  alter the text of  the message in
some way and resend  it to the list. Note that altering  the
"Subject:" line or adding blank lines at  the top or bottom of the
message  is not sufficient; you should  instead add  a  sentence or
two  at  the top  explaining  why you  are resending the  message, so
that the  other subscribers understand why  they are getting two
copies of the same message.

--------------

Despite these error messages the mails are distributed correctly. So
it is not a major problem but still irritating.

Even more, from time to time there are mails in the list which appear
twice identically.

Any idea what to do? Thank you very much in advance!
Erwin