There is no information here. There is nothing we could tell you without
knowing Outlook version, mail transport type, how the DL was created and how
the DL was selected as a recipient.

I am also having the same problem. I recently upgraded from Outlook Express
to Outlook. At first I thought it had something to do with when I transferred
the details across, so I deleted the DL & reloaded the contacts under a new
DL name.
Same thing happened. The contacts are receiving two emails, one of which is
fine, the other is a heap of heiroglyphics.
My new computer also gives the option of having multiple users and I am
wondering if the addresses are doubling up somewhere.
Like Chris, I urgently need assistance, and the people in the DL are
thinking I am sending them a virus.
Sue