|It could be that they went to a secure authentication. Try going to Tools -> Acounts Settings -> Change -> More Settings -> Advanced and check on the "This server requires encrypted connection SSL". I had an ISP do this to me once. |
Otherwise you have a firewall blocking SMTP and/or POP. Get a Laptop -> Turn off Windows Firewall and Symantec -> Try it on a regular wire if it fails then hook the laptop into your DMZ and try again. If it fails there then call your ISP.