Topic: Attachments inaccessble in webmail

[wyron]

I have a user (a friend with a webpage and a mailaccount for webmail hosted on my server), who has confronted me with an annoying problem.
Attachments in his INBOX cannot be downloaded or opened.
The tricky part ?
The mailsetup also forwards all his mail to a Mailbox at his work, and there he has no problem opening the attachments.
His account is the only one with this problem.
This is a little beyond me ??????