Oh, we’ve seen this one before!
There are three possible explanations:
1) This occurs when the recipient is listed in the Address Book without a SHORTNAME in the Person Doc. The server apparently tries and fails to resolve a useable address. The fix for this is to simply add the full internet address (email@example.com) into the shortname field. Then when the email goes outside your domain, it’s got a correct address to refer to.
This is the most likely cause if a lot of people in your organzation are having the problem. You may have to take a look at the Admin-P processes that update information in your address book.
2) This occurs when the user’s name has been cut short or is otherwise incorrect in the Calendar Profile/Owner’s Field. To correct, simply select user’s name from the Address Book link beside that field.
This CAN be widespread if there’s a problem with your updating process.
3) This can occur when the user’s ID fails to update. The clue here is that the outgoing emails will be both from the user’s account and have a “Sent by: (user name)” line. This is because the user’s ID and their mailfile owner’s field do not match — in this case, the Owner’s field is fine; the ID has problems.
This last scenario is the least likely for your situation, because this usually happens to only an odd person here and there in an organization.
Hope this helps.