I changed my password (outgoing/incoming - same). Outgoing works, incoming doesn't.

I changed my password for AT&T (Yahoo?). I had changed the password previously (about a week ago). Both incoming and outgoing server passwords are the same. After I changed this time, the I could not receive emails through Tbird, but I could directly from the email server. I can send emails via Tbird through the outgoing server, though. Since the password is the same for outgoing and incoming, I can't see why one doesn't work and the other does.