I have recently encountered a problem where my email program, Thunderbird, is attempting to send emails seemingly on its own. I have included a screen shot of why I am seeing. This happens infrequently. It seems to be trying to send messages to accounts that no longer active. They seem to be related to old mailing lists that I have not used for a very long time. I have even deleted them but still get this messages from time to time.

I am running Windows Xp Pro. Have all security updates applied. I am using ESET Smart Security, version 4.2 for virus protection. It is up to date and when I run a scan it indicates that everything is okay. As indicated I am using Thunerbird for email and it is up to date
Any thoughts on what might be going on here?

Thanks

Replaced doc file with jpeg. Hope this is better.

I'm not really ready to open .doc file from unknown computer.
Attach a screenshot in graphic format (gif, jpeg).