FortiClient mail crashed (outlook 2007)

I have problem with reciving some mails especially with attachment file like "jpg or pdf" beginning of those mails start with:

X-Virus-Scanned: Debian amavisd-new at --------------

X-Spam-Flag: NO

X-Spam-Score: -1.899

X-Spam-Level:

X-Spam-Status: No, score=-1.899 required=4.3 tests=[BAYES_00=-1.9, It only happend on POP3 not on IMAP any solutions on it? Edit: I think it's some problem with MIME because I find in every mail this: "This is a multipart message in MIME format."