they seem to be blocking port 25 and since this is the standard SMTP port, there's not much you can do about it --
are you sure that using the company's SMTP server doesn't get you anywhere?
also: i suppose the ip address in your post, is one of your companies' -- first of all, i hope your tech department doesn't read these posts, since they might not be so happy about you giving away their ip address -- but, we're all nice people here, so, we won't do harm -- anyway, i guess that means that your company is concentric.net -- why don't you try one of these domainnames as your smtp entry:
buckpalace.concentric.net
mailhost.concentric.net
franklin.concentric.net
beasley.concentric.net
morse.concentric.net
overflow.concentric.net
just make sure you're not violating company policies, ok?
if all this fails, the only option would be to find an SMTP server that accepts mail on another port than 25 -- most proxy servers don't block ports over port 1024....
hope you figure it out --
good luck