attach picture and file distorted

I have Windows server 2008 and domain base network. My network is working perfectly except one thing.

When ever some body send me e-mail attached with picture or pdf file it appear distorted or patchy. I talk to my smtp server host and they are saying port **80 and 443** is scan and sucking my mail. i turn off all firewall and allow inbound and out bound connection full access but still no solution.

Please if some body have any idea or solution feel free to buss me.

Thank you