sendmail and virtualusers

[Noah]

freebsd-4.9
sendmail-sasl-8.13.1

I am finding a strange problem where I am multihosting multiple domains and
have multiple virtualusers in /etc/mail/virtualusers that exist in many
different domains.

I have one entry for mail to domain1.com - looks like this:

--- snip ---

###domain1.com
com at domain1.com     user1

--- snip ---

but when I send mail to blah at domain1.com I thought it would bounce but instead
it appears in my personal mailbox with the username user2 (user1 is a
different account).  I am even sending mail from a remote machine.

I cant figure out why it is delivered to me and also cant figure out why a
bounce is not sent to the originator.

any clues here?

cheers,

Noah