I'm using my laptop away from home (in SE Asia) and none of my ntlworld.com addresses can connect to the smtp server via Thunderbird. I've checked and rechecked all the settings - smtp.virginmedia.com - full email address - 465 - ssl etc. Incoming is fine and I can send via webmail but that's very inconvenient. Any ideas? Has my IP address been blocked?
No your IP address has not likely been blocked. But you are in an area where spammers and spam sending is prevalent and VM apply very strict and very low limits on the amount of outgoing mail allowed from a non-VM IP in such areas in an effort to prevent spamming. The counter resets every 24 hours and each recipient in each mail counts as one mail. Your only alternative is to use web mail where the sending limits are much higher because it is more difficult for spammers to use web mail to spam.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.