gillyd said:
gillyd
Firstly, thanks for taking the time to respond. I'm using Outlook
2003 - Exchange 6.5 - do you need any other info?
Since you're in a company network, why not block outbound all e-mail
traffic (ports 25, 587, 110 465, 995) at the company's network boundary
in their firewall appliance? The Exchange server would be within the
company's network. All the other mail hosts would be outside and have
to get past the firewall.
Some e-mail servers now use port 80 to get around the firewall blocking.
You'd have to use a list of blocked hostnames to prevent them from
getting to outside mail hosts. I've never been involved with Websense
but they might have a category (that your company could block) that
lists mail servers. For example, I use OpenDNS as my DNS service
instead of my ISP's DNS server. One of their categories is "Webmail" so
you could block your users from getting to webmail providers. I don't
see them listing POP/IMAP mail hosts but that doesn't mean Websense
doesn't. OpenDNS is free. Websense costs money.