Uninstalling and reinstalling TB program will have no effect on your issue.

I'm presuming you can send to any other email address. If yes, then there is no problem with Thunderbird.

Test: If you use webmail account via a browser to send an email to one of those particular email addresses, does it get through to recipient?

If you send an email via Thunderbird to one of those particular email addresses, what happens ? Does the email say it has been sent and you have a copy in your 'Sent' folder? Do you get a bounced back message from Mailor daemon ? If yes, what does it say...word for word?

Thanks for your help. However my problem is still unsolved. I sent an email today to a friend with the ".twcny.rr.com" address. I sent it from TBird and from my Time Warner web mail account. The web mail message went through. The Tbird message did not. There was no "undeliverable" message. The Tbird message did appear in my "sent" box, as well as a copy. My email is also a ".twcny.rr.com" address.

The difference is that the one from TB will be using the smtp server and also will be sent using your computers IP address.

This sounds like the emails are being sent, but are being filtered off as if they are being caught by a TWc server applied Spam Filter or they are being received by correct email address and being placed in that accounts 'Spam' folder.

It would seem a bit odd for all the ".twcny.rr.com" email addresses to be placing all your emails in the various Spam folders and anyway the recipients could have checked.

As you can send perfectly ok to any other email address, clearly there is nothing wrong with the smtp outgoing server.

It seems that you are being blocked by TWC. Try the info at this link to test: http://postmaster.rr.com/amIBlockedByRR

Seems to be solved. Thanks for your help.