The mailing list for listmasters using Sympa

[address@concealed]

I've noticed that there are repeated messages when sending mail both  
to a list and to a person who is subscriber of that list.

Assuming address@concealed is my email address and i'm subscribed at  
list address@concealed with the same address, when someone sends a  
mail with the following header, I receive this mail twice.

FROM:   XXX
TO:     address@concealed, address@concealed

Is there any way to configure the mail list server (sympa) to receive  
this mail once? Can Sympa check if the addresses at the header are  
subscriber of the list, and then decide what to do?

Adib.