Question : Exchange 2003 with primary and secondary email address dropping attachments to one or the other address

I have an Exchange 2003 server with users using Outlook 2003 client software. my users can email attachments to another Exchange 2003 server with multiple stores. Their users have a primary and a secondary email address. We can send the same email w/attachment to their user using both of that users email addresses. One email will drop the attachment but the other one receives it fine. They can be sent in the same email or separately.

Answer : Exchange 2003 with primary and secondary email address dropping attachments to one or the other address

Yes, the misconfig is definitely at their side. Even if you wanted you couldn't make it happen from the sending side without their "help". Most people with poor knowledge will always blame others. Easy "solution"