Outlook 2003 attachments corrupted

Hi,
when sending a mail with a pdf file, word document,… as attachment using outlook 2003, the recipient receives the attachment as a 4Kb size document or pdf although the original one was more than 100 Kb. In the sent items of the user, it is 4 Kb too.

I would be grateful if you could help me on this issue.

Thanking you in advance