Security issue (sending password in a plain text)

After registration I have received welcome email. That's okay. But my concern are informations sent in that message, namely a password in a plain text. I don't know how the things are when we recover a password. In that case we shouldn't be sent our password in plain text, but sent a new (temporary) password or a password resetting link.
It may sound paranoid, but imagine how dangerous could be such a mail left in a mailbox, when someone uses that password in other places on the Internet.