Web Mail (hotmail, yahoo, netaddress ...) with Attachment doesn't work

[tho...@tang.ca]

Hi All

My company has about twenty PC connecting internet through Bell AsdL, there
is a firewall device (sonicwall) between DSL modem and Hub.

firewall setting is :
deny WAN to LAN and
enable LAN to WAN access

One week ago everything is OK, but this week all of computer can not send
email with a attachment file through hotmail, yahoo, netaddress etc.
Webemail.
I don't know why, who can help me.

Thanks