The mailing list for listmasters using Sympa

[Paul Wisén <address@concealed>]

Is there a way, as a owner of a list, to, via email, add a new
subscriber and have sympa check if it's not already subscribed ?
And, if it is already subscribe to do nothing, or maybe complain a bit
and if its not already subscribed to subscribe it and send the welcome
message ?

That check works over wwsympa but, as far as I see not when I do add
list email .. 
I can add myself multiple times and I get the welcome message everytime,
witch is not good. 

Any ideas?
Can't find it in the docs.
I'm running sympa 3.3.3 

/Paul