Geraldo Xexeo <GXEXEO@CERNVM> writes ...
>
>  By the way, which problems can make a list to repeat one mail
>twice to all its users? (This is a common question?)
 
There are probably lots of reasons, but I had one a few months ago.  A
subscriber happened to be on an MVS system (IRISHMVS.BITNET).  That
system delivered the mail and returned a copy to the list in such a way
that it looked like a new posting to LISTSERV.  The problem at that site
was rectified once recognized.