Mailing List Web Interface

Why can not I send outgoing mail through the web interface?
Mail allows me to connect and check mail, but each When I try to send mail (a Yahoo group list), I asked for my password, then sends me back to the homepage without sending the e-mail my message. Yes, the window composition shows I'm connected when I came to send, and yes, I am available to stay connected, I tried four times to send a message and each time I asked for paassword then reversed on the email compose page.
I want to know why not send my mail !!!!!
Eric Meyer interviewed at Web 2.0 Expo New York 2010