Outlook 2000 question

Hi there,
Why when you’re sending an email to more than one person and one of the emails is wrong the email sometimes then get stuck in the outbox and doesn’t get send at all and sometimes the message is sent and then you get a mail delivery failure for the ones where the email addresses was wrong. It’s just sometimes we have a list and then if just one emailaddress is wrong it doesn’t want to send the email to the rest of the recipients either.
Hope someone can help. Many thanks.