How can i prevent dubble e-mail.

When 1 e-mail is sent to more than one person in the same domain all persons receive multiple mails
i`ve sent 1-email to bla@mydomain.com, blabla@mydomain.com, me@mydomain.com (non existing accounts, fetchall)
Since i have the last resort account this mail is recieved 9 times in my account.

If i repeat this action and before running fetchmail i delete 2 out of three messages at my hosting provider (webmail) i only recieve 3 messages.

fetchmails polls the fetchall account and passes this throug to postfix postfix passes this throug to my local (commercial) mda.

is there a way to delete dubble (identical) mail before fetchmail fetches my mail (automaticaly of course) or can i configure fetchmail to only look at the first adress without having the risk of 1 person getting 3 mails and the other 2 getting nothing

thanks
Daniel