one mac in office sends pdfs, jpgs, xls files as attachments, but the recipients cannot open them.
The email account is a pop account.
the attachments can be opened by the user before he sends them.
but once received, they arrive as attachments, with same file size, but cannot be opened or saved locally from outlook.

the same user gets this problem as well, if he tries to open the attachment from the email that is in his sent items too.