Can I ask which ISP you use ?
Just that when I was with Freeserve (later owned by Wanadoo, now owned by Orange) they trapped any outgoing e-mail and fed it via their own mail server.
As well as using an internet address (like a phone number) to connect to a service, there are "port numbers" too. A bit like phoning a big company and asking for "extension 123" to reach accounts, or "extension 234" for customer services.
Port 110 is used to collect POP email from a server
Port 25 is used to send mail via an SMTP server
Freeserve used to force any "port 25" traffic into their own server (ie ignoring the use of any "external" IP address or server name). They did it to block spam, and had their own [unpublished] rules (so if you sent a party invitiation to 20 people it would be swallowed as spam, if you sent to 10 or 12 it would go OK).
So, depending on your ISP, connection might be blocked between you and smtp.ukservers.net (the Virtualnames mail server) on port 25