>One of my subscriber who uses an internet access through a
>BBS gets normally  the mails but cannot send any message
>to the list.
 
Basically, their e-mail service providor (most likely) has NOT
properly configured their SENDMAIL parameters.  The FROM: field
is not RFC821/822 compliant.  This probably is not the user's
or your fault.  They need to contact their postmaster.
 
>Each time she tries, she receives back the following
>message:
 
 
>     ----- Transcript of session follows -----
> MAIL From:<atlmug.org!Caroline_I._Widmer>
>501 Syntax Error. Missing Domain Name
>554 emory!SJUVM.STJOHNS.EDU!SPIRAMED... Remote protocol
>error