How to get rid of 'BOUNCE <listname>: Non-member submission from'

["Willem-Jan Vroom" <w . vroom @ hccnet . nl>]

Hello,

I a using a Majordomo mailinglist at my hostingprovider.

Now, if somebody sents a message to the mailinglist who is not subscribed, I
receive a BOUNCE message. Now, I do not want to receive such a message or
that such a message is sent. How do I get rid of them?

Of course I can use procmail to delete messages but my current hosting
provider does not support procmail. 

Any help is appreciated.

With kind regards,
Willem-Jan